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119-890: Intel Agilex FPGAs initially focused on performance applications such as data center processing, but the brand has been expanded to include several new series of Agilex FPGAs which have different characteristics, such as lower power and lower logic densities, in order to fit an even wider range of applications. As a result, the Agilex brand is combined with a numerical suffix to organize various FPGA product series into different families of FPGAs and SoC FPGAs. The Agilex 9 family are FPGAs targeted at Direct RF applications and include wideband data converters with sample rates up to 64Gsps and medium-band data converters with hi-fidelity performance. The initial family of Agilex FPGAs and SoC FPGAs which began shipping in 2019 were rebranded as Agilex 7 in January 2023 as

238-461: A memory cell , usually consisting of a tiny capacitor and a transistor , both typically based on metal–oxide–semiconductor (MOS) technology. While most DRAM memory cell designs use a capacitor and transistor, some only use two transistors. In the designs where a capacitor is used, the capacitor can either be charged or discharged; these two states are taken to represent the two values of a bit, conventionally called 0 and 1. The electric charge on

357-501: A bipolar dynamic RAM for its electronic calculator Toscal BC-1411. In 1966, Tomohisa Yoshimaru and Hiroshi Komikawa from Toshiba applied for a Japanese patent of a memory circuit composed of several transistors and a capacitor, in 1967 they applied for a patent in the US. The earliest forms of DRAM mentioned above used bipolar transistors . While it offered improved performance over magnetic-core memory , bipolar DRAM could not compete with

476-466: A cost advantage that grew with every jump in memory size. The MK4096 proved to be a very robust design for customer applications. At the 16 Kbit density, the cost advantage increased; the 16 Kbit Mostek MK4116 DRAM, introduced in 1976, achieved greater than 75% worldwide DRAM market share. However, as density increased to 64 Kbit in the early 1980s, Mostek and other US manufacturers were overtaken by Japanese DRAM manufacturers, which dominated

595-852: A customer reaches foundry tapeout or prototyping. 75% of ARM's most recent IP over the last two years are included in ARM Flexible Access. As of October 2019: Arm provides a list of vendors who implement ARM cores in their design (application specific standard products (ASSP), microprocessor and microcontrollers). ARM cores are used in a number of products, particularly PDAs and smartphones . Some computing examples are Microsoft 's first generation Surface , Surface 2 and Pocket PC devices (following 2002 ), Apple 's iPads , and Asus 's Eee Pad Transformer tablet computers , and several Chromebook laptops. Others include Apple's iPhone smartphones and iPod portable media players , Canon PowerShot digital cameras , Nintendo Switch hybrid,

714-820: A design service foundry offers lower overall pricing (through subsidisation of the licence fee). For high volume mass-produced parts, the long term cost reduction achievable through lower wafer pricing reduces the impact of ARM's NRE ( non-recurring engineering ) costs, making the dedicated foundry a better choice. Companies that have developed chips with cores designed by Arm include Amazon.com 's Annapurna Labs subsidiary, Analog Devices , Apple , AppliedMicro (now: MACOM Technology Solutions ), Atmel , Broadcom , Cavium , Cypress Semiconductor , Freescale Semiconductor (now NXP Semiconductors ), Huawei , Intel , Maxim Integrated , Nvidia , NXP , Qualcomm , Renesas , Samsung Electronics , ST Microelectronics , Texas Instruments , and Xilinx . In February 2016, ARM announced

833-437: A hard-wired dynamic memory. Paper tape was read and the characters on it "were remembered in a dynamic store." The store used a large bank of capacitors, which were either charged or not, a charged capacitor representing cross (1) and an uncharged capacitor dot (0). Since the charge gradually leaked away, a periodic pulse was applied to top up those still charged (hence the term 'dynamic')". In November 1965, Toshiba introduced

952-799: A lawsuit settlement, and Intel took the opportunity to supplement their i960 line with the StrongARM. Intel later developed its own high performance implementation named XScale , which it has since sold to Marvell . Transistor count of the ARM core remained essentially the same throughout these changes; ARM2 had 30,000 transistors, while ARM6 grew only to 35,000. In 2005, about 98% of all mobile phones sold used at least one ARM processor. In 2010, producers of chips based on ARM architectures reported shipments of 6.1 billion ARM-based processors , representing 95% of smartphones , 35% of digital televisions and set-top boxes , and 10% of mobile computers . In 2011,

1071-412: A logic one requires the wordline be driven to a voltage greater than the sum of V CC and the access transistor's threshold voltage (V TH ). This voltage is called V CC pumped (V CCP ). The time required to discharge a capacitor thus depends on what logic value is stored in the capacitor. A capacitor containing logic one begins to discharge when the voltage at the access transistor's gate terminal

1190-504: A merchant foundry that holds an ARM licence, such as Samsung or Fujitsu, can offer fab customers reduced licensing costs. In exchange for acquiring the ARM core through the foundry's in-house design services, the customer can reduce or eliminate payment of ARM's upfront licence fee. Compared to dedicated semiconductor foundries (such as TSMC and UMC ) without in-house design services, Fujitsu/Samsung charge two- to three-times more per manufactured wafer . For low to mid volume applications,

1309-547: A quirk of the 6502's design, the CPU left the memory untouched for half of the time. Thus by running the CPU at 1 MHz, the video system could read data during those down times, taking up the total 2 MHz bandwidth of the RAM. In the BBC Micro, the use of 4 MHz RAM allowed the same technique to be used, but running at twice the speed. This allowed it to outperform any similar machine on

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1428-455: A ready-to-manufacture verified semiconductor intellectual property core . For these customers, Arm Holdings delivers a gate netlist description of the chosen ARM core, along with an abstracted simulation model and test programs to aid design integration and verification. More ambitious customers, including integrated device manufacturers (IDM) and foundry operators, choose to acquire the processor IP in synthesizable RTL ( Verilog ) form. With

1547-671: A simple chip design could nevertheless have extremely high performance, much higher than the latest 32-bit designs on the market. The second was a visit by Steve Furber and Sophie Wilson to the Western Design Center , a company run by Bill Mensch and his sister, which had become the logical successor to the MOS team and was offering new versions like the WDC 65C02 . The Acorn team saw high school students producing chip layouts on Apple II machines, which suggested that anyone could do it. In contrast,

1666-514: A single bitline contact) from a column, then move the DRAM cells from an adjacent column into the voids. The location where the bitline twists occupies additional area. To minimize area overhead, engineers select the simplest and most area-minimal twisting scheme that is able to reduce noise under the specified limit. As process technology improves to reduce minimum feature sizes, the signal to noise problem worsens, since coupling between adjacent metal wires

1785-407: A single chip, to accommodate more capacity without becoming too slow. When such a RAM is accessed by clocked logic, the times are generally rounded up to the nearest clock cycle. For example, when accessed by a 100 MHz state machine (i.e. a 10 ns clock), the 50 ns DRAM can perform the first read in five clock cycles, and additional reads within the same page every two clock cycles. This

1904-546: A small team to design the actual processor based on Wilson's ISA. The official Acorn RISC Machine project started in October 1983. Acorn chose VLSI Technology as the "silicon partner", as they were a source of ROMs and custom chips for Acorn. Acorn provided the design and VLSI provided the layout and production. The first samples of ARM silicon worked properly when first received and tested on 26 April 1985. Known as ARM1, these versions ran at 6 MHz. The first ARM application

2023-434: A special case; not only are they allowed to sell finished silicon containing ARM cores, they generally hold the right to re-manufacture ARM cores for other customers. Arm Holdings prices its IP based on perceived value. Lower performing ARM cores typically have lower licence costs than higher performing cores. In implementation terms, a synthesisable core costs more than a hard macro (blackbox) core. Complicating price matters,

2142-462: A time determined by an external timer function that governs the operation of the rest of a system, such as the vertical blanking interval that occurs every 10–20 ms in video equipment. The row address of the row that will be refreshed next is maintained by external logic or a counter within the DRAM. A system that provides the row address (and the refresh command) does so to have greater control over when to refresh and which row to refresh. This

2261-444: A value is read, modified, and then written back as a single, indivisible operation (Jacob, p. 459). The one-transistor, zero-capacitor (1T, or 1T0C) DRAM cell has been a topic of research since the late-1990s. 1T DRAM is a different way of constructing the basic DRAM memory cell, distinct from the classic one-transistor/one-capacitor (1T/1C) DRAM cell, which is also sometimes referred to as 1T DRAM , particularly in comparison to

2380-820: A variety of licensing terms, varying in cost and deliverables. Arm Holdings provides to all licensees an integratable hardware description of the ARM core as well as complete software development toolset ( compiler , debugger , software development kit ), and the right to sell manufactured silicon containing the ARM CPU. SoC packages integrating ARM's core designs include Nvidia Tegra's first three generations, CSR plc's Quatro family, ST-Ericsson's Nova and NovaThor, Silicon Labs's Precision32 MCU, Texas Instruments's OMAP products, Samsung's Hummingbird and Exynos products, Apple's A4 , A5 , and A5X , and NXP 's i.MX . Fabless licensees, who wish to integrate an ARM core into their own chip design, are usually only interested in acquiring

2499-469: A visit to another design firm working on modern 32-bit CPU revealed a team with over a dozen members who were already on revision H of their design and yet it still contained bugs. This cemented their late 1983 decision to begin their own CPU design, the Acorn RISC Machine. The original Berkeley RISC designs were in some sense teaching systems, not designed specifically for outright performance. To

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2618-450: Is 3-4-4-8 with a 200 MHz clock, while premium-priced high performance PC3200 DDR DRAM DIMM might be operated at 2-2-2-5 timing. Minimum random access time has improved from t RAC  = 50 ns to t RCD + t CL = 22.5 ns , and even the premium 20 ns variety is only 2.5 times faster than the asynchronous DRAM. CAS latency has improved even less, from t CAC = 13 ns to 10 ns. However,

2737-407: Is volatile memory (vs. non-volatile memory ), since it loses its data quickly when power is removed. However, DRAM does exhibit limited data remanence . DRAM typically takes the form of an integrated circuit chip, which can consist of dozens to billions of DRAM memory cells. DRAM chips are widely used in digital electronics where low-cost and high-capacity computer memory is required. One of

2856-658: Is a family of RISC instruction set architectures (ISAs) for computer processors . Arm Holdings develops the ISAs and licenses them to other companies, who build the physical devices that use the instruction set. It also designs and licenses cores that implement these ISAs. Due to their low costs, low power consumption, and low heat generation, ARM processors are useful for light, portable, battery-powered devices, including smartphones , laptops , and tablet computers , as well as embedded systems . However, ARM processors are also used for desktops and servers , including Fugaku ,

2975-442: Is able to offer better long-term area efficiencies; since folded array architectures require increasingly complex folding schemes to match any advance in process technology. The relationship between process technology, array architecture, and area efficiency is an active area of research. The first DRAM integrated circuits did not have any redundancy. An integrated circuit with a defective DRAM cell would be discarded. Beginning with

3094-439: Is above V CCP . If the capacitor contains a logic zero, it begins to discharge when the gate terminal voltage is above V TH . Up until the mid-1980s, the capacitors in DRAM cells were co-planar with the access transistor (they were constructed on the surface of the substrate), thus they were referred to as planar capacitors. The drive to increase both density and, to a lesser extent, performance, required denser designs. This

3213-413: Is done to minimize conflicts with memory accesses, since such a system has both knowledge of the memory access patterns and the refresh requirements of the DRAM. When the row address is supplied by a counter within the DRAM, the system relinquishes control over which row is refreshed and only provides the refresh command. Some modern DRAMs are capable of self-refresh; no external logic is required to instruct

3332-436: Is fully at its highest voltage and the other bit-line is at the lowest possible voltage. To store data, a row is opened and a given column's sense amplifier is temporarily forced to the desired high or low-voltage state, thus causing the bit-line to charge or discharge the cell storage capacitor to the desired value. Due to the sense amplifier's positive feedback configuration, it will hold a bit-line at stable voltage even after

3451-405: Is given as n F , where n is a number derived from the DRAM cell design, and F is the smallest feature size of a given process technology. This scheme permits comparison of DRAM size over different process technology generations, as DRAM cell area scales at linear or near-linear rates with respect to feature size. The typical area for modern DRAM cells varies between 6–8 F . The horizontal wire,

3570-424: Is inversely proportional to their pitch. The array folding and bitline twisting schemes that are used must increase in complexity in order to maintain sufficient noise reduction. Schemes that have desirable noise immunity characteristics for a minimal impact in area is the topic of current research (Kenner, p. 37). Advances in process technology could result in open bitline array architectures being favored if it

3689-408: Is limited by its capacitance (which increases with length), which must be kept within a range for proper sensing (as DRAMs operate by sensing the charge of the capacitor released onto the bitline). Bitline length is also limited by the amount of operating current the DRAM can draw and by how power can be dissipated, since these two characteristics are largely determined by the charging and discharging of

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3808-489: Is the clearest way to compare between the performance of different DRAM memories, as it sets the slower limit regardless of the row length or page size. Bigger arrays forcibly result in larger bit line capacitance and longer propagation delays, which cause this time to increase as the sense amplifier settling time is dependent on both the capacitance as well as the propagation latency. This is countered in modern DRAM chips by instead integrating many more complete DRAM arrays within

3927-443: Is usually arranged in a rectangular array of charge storage cells consisting of one capacitor and transistor per data bit. The figure to the right shows a simple example with a four-by-four cell matrix. Some DRAM matrices are many thousands of cells in height and width. The long horizontal lines connecting each row are known as word-lines. Each column of cells is composed of two bit-lines, each connected to every other storage cell in

4046-447: The Intel 1103 , in October 1970, despite initial problems with low yield until the fifth revision of the masks . The 1103 was designed by Joel Karp and laid out by Pat Earhart. The masks were cut by Barbara Maness and Judy Garcia. MOS memory overtook magnetic-core memory as the dominant memory technology in the early 1970s. The first DRAM with multiplexed row and column address lines was

4165-468: The JEDEC standard. Some systems refresh every row in a burst of activity involving all rows every 64 ms. Other systems refresh one row at a time staggered throughout the 64 ms interval. For example, a system with 2  = 8,192 rows would require a staggered refresh rate of one row every 7.8 μs which is 64 ms divided by 8,192 rows. A few real-time systems refresh a portion of memory at

4284-490: The Mostek MK4096 4 Kbit DRAM designed by Robert Proebsting and introduced in 1973. This addressing scheme uses the same address pins to receive the low half and the high half of the address of the memory cell being referenced, switching between the two halves on alternating bus cycles. This was a radical advance, effectively halving the number of address lines required, which enabled it to fit into packages with fewer pins,

4403-596: The PC ). The ARM2 had a transistor count of just 30,000, compared to Motorola's six-year-older 68000 model with around 68,000. Much of this simplicity came from the lack of microcode , which represents about one-quarter to one-third of the 68000's transistors, and the lack of (like most CPUs of the day) a cache . This simplicity enabled the ARM2 to have a low power consumption and simpler thermal packaging by having fewer powered transistors. Nevertheless, ARM2 offered better performance than

4522-680: The Wii security processor and 3DS handheld game consoles , and TomTom turn-by-turn navigation systems . In 2005, Arm took part in the development of Manchester University 's computer SpiNNaker , which used ARM cores to simulate the human brain . ARM chips are also used in Raspberry Pi , BeagleBoard , BeagleBone , PandaBoard , and other single-board computers , because they are very small, inexpensive, and consume very little power. The 32-bit ARM architecture ( ARM32 ), such as ARMv7-A (implementing AArch32; see section on Armv8-A for more on it),

4641-454: The cache memories in processors . The need to refresh DRAM demands more complicated circuitry and timing than SRAM. This complexity is offset by the structural simplicity of DRAM memory cells: only one transistor and a capacitor are required per bit, compared to four or six transistors in SRAM. This allows DRAM to reach very high densities with a simultaneous reduction in cost per bit. Refreshing

4760-404: The /RAS low to valid data out time. This is the time to open a row, settle the sense amplifiers, and deliver the selected column data to the output. This is also the minimum /RAS low time, which includes the time for the amplified data to be delivered back to recharge the cells. The time to read additional bits from an open page is much less, defined by the /CAS to /CAS cycle time. The quoted number

4879-468: The 32-bit ARM architecture was the most widely used architecture in mobile devices and the most popular 32-bit one in embedded systems. In 2013, 10 billion were produced and "ARM-based chips are found in nearly 60 percent of the world's mobile devices". Arm Holdings's primary business is selling IP cores , which licensees use to create microcontrollers (MCUs), CPUs , and systems-on-chips based on those cores. The original design manufacturer combines

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4998-504: The 3T and 4T DRAM which it replaced in the 1970s. In 1T DRAM cells, the bit of data is still stored in a capacitive region controlled by a transistor, but this capacitance is no longer provided by a separate capacitor. 1T DRAM is a "capacitorless" bit cell design that stores data using the parasitic body capacitance that is inherent to silicon on insulator (SOI) transistors. Considered a nuisance in logic design, this floating body effect can be used for data storage. This gives 1T DRAM cells

5117-464: The 3T1C cell for performance reasons (Kenner, p. 6). These performance advantages included, most significantly, the ability to read the state stored by the capacitor without discharging it, avoiding the need to write back what was read out (non-destructive read). A second performance advantage relates to the 3T1C cell's separate transistors for reading and writing; the memory controller can exploit this feature to perform atomic read-modify-writes, where

5236-462: The 64 Kbit generation, DRAM arrays have included spare rows and columns to improve yields. Spare rows and columns provide tolerance of minor fabrication defects which have caused a small number of rows or columns to be inoperable. The defective rows and columns are physically disconnected from the rest of the array by a triggering a programmable fuse or by cutting the wire by a laser. The spare rows or columns are substituted in by remapping logic in

5355-752: The ARM core with other parts to produce a complete device, typically one that can be built in existing semiconductor fabrication plants (fabs) at low cost and still deliver substantial performance. The most successful implementation has been the ARM7TDMI with hundreds of millions sold. Atmel has been a precursor design center in the ARM7TDMI-based embedded system. The ARM architectures used in smartphones, PDAs and other mobile devices range from ARMv5 to ARMv8-A . In 2009, some manufacturers introduced netbooks based on ARM architecture CPUs, in direct competition with netbooks based on Intel Atom . Arm Holdings offers

5474-584: The ARM instruction sets. These cores must comply fully with the ARM architecture. Companies that have designed cores that implement an ARM architecture include Apple, AppliedMicro (now: Ampere Computing ), Broadcom, Cavium (now: Marvell), Digital Equipment Corporation , Intel, Nvidia, Qualcomm, Samsung Electronics, Fujitsu , and NUVIA Inc. (acquired by Qualcomm in 2021). On 16 July 2019, ARM announced ARM Flexible Access. ARM Flexible Access provides unlimited access to included ARM intellectual property (IP) for development. Per product licence fees are required once

5593-671: The ARM6, first released in early 1992. Apple used the ARM6-based ARM610 as the basis for their Apple Newton PDA. In 1994, Acorn used the ARM610 as the main central processing unit (CPU) in their RiscPC computers. DEC licensed the ARMv4 architecture and produced the StrongARM . At 233  MHz , this CPU drew only one watt (newer versions draw far less). This work was later passed to Intel as part of

5712-531: The Agilex 7 FPGA and are generally considered mid-range FPGAs. The Agilex 5 SoC FPGA variants include an ARM Cortex A76/A55 quad core hard processor system. The Agilex 3 family are power and cost optimized FPGAs that deliver relatively high performance for this class of FPGA. The Agilex 3 SoC FPGA variants offer an ARM Cortex A55 dual core hard processor system. ARM architecture family ARM (stylised in lowercase as arm , formerly an acronym for Advanced RISC Machines and originally Acorn RISC Machine )

5831-462: The Agilex brand was broadened to cover additional FPGA families by using a numerical suffix. Agilex 7 FPGAs are a family of high-performance FPGAs with a focus on delivering industry-leading logic fabric and I/O speeds and targeted at bandwidth- and compute-intensive applications. The Agilex 7 SoC FPGA variants include an ARM Cortex-A53 quad core hard processor system. The Agilex 5 family are FPGAs and SoC FPGAs with lower power and logic densities than

5950-578: The Built on ARM Cortex Technology licence, often shortened to Built on Cortex (BoC) licence. This licence allows companies to partner with ARM and make modifications to ARM Cortex designs. These design modifications will not be shared with other companies. These semi-custom core designs also have brand freedom, for example Kryo 280 . Companies that are current licensees of Built on ARM Cortex Technology include Qualcomm . Companies can also obtain an ARM architectural licence for designing their own CPU cores using

6069-419: The CPU can be in only one mode, but it can switch modes due to external events (interrupts) or programmatically. The original (and subsequent) ARM implementation was hardwired without microcode , like the much simpler 8-bit 6502 processor used in prior Acorn microcomputers. The 32-bit ARM architecture (and the 64-bit architecture for the most part) includes the following RISC features: To compensate for

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6188-401: The CPU designs available. Their conclusion about the existing 16-bit designs was that they were a lot more expensive and were still "a bit crap", offering only slightly higher performance than their BBC Micro design. They also almost always demanded a large number of support chips to operate even at that level, which drove up the cost of the computer as a whole. These systems would simply not hit

6307-498: The DDR3 memory does achieve 32 times higher bandwidth; due to internal pipelining and wide data paths, it can output two words every 1.25 ns (1 600  Mword/s) , while the EDO DRAM can output one word per t PC  = 20 ns (50 Mword/s). Each bit of data in a DRAM is stored as a positive or negative electrical charge in a capacitive structure. The structure providing

6426-439: The DRAM chip. Berkeley's design did not consider page mode and treated all memory equally. The ARM design added special vector-like memory access instructions, the "S-cycles", that could be used to fill or save multiple registers in a single page using page mode. This doubled memory performance when they could be used, and was especially important for graphics performance. The Berkeley RISC designs used register windows to reduce

6545-514: The DRAM chips in them), such as Kingston Technology , and some manufacturers that sell stacked DRAM (used e.g. in the fastest supercomputers on the exascale ), separately such as Viking Technology . Others sell such integrated into other products, such as Fujitsu into its CPUs, AMD in GPUs, and Nvidia , with HBM2 in some of their GPU chips. The cryptanalytic machine code-named Aquarius used at Bletchley Park during World War II incorporated

6664-400: The DRAM to refresh or to provide a row address. Under some conditions, most of the data in DRAM can be recovered even if the DRAM has not been refreshed for several minutes. Many parameters are required to fully describe the timing of DRAM operation. Here are some examples for two timing grades of asynchronous DRAM, from a data sheet published in 1998: Thus, the generally quoted number is

6783-444: The PC and the status flags. This decision halved the interrupt overhead. Another change, and among the most important in terms of practical real-world performance, was the modification of the instruction set to take advantage of page mode DRAM . Recently introduced, page mode allowed subsequent accesses of memory to run twice as fast if they were roughly in the same location, or "page", in

6902-618: The RISC's basic register-heavy and load/store concepts, ARM added a number of the well-received design notes of the 6502. Primary among them was the ability to quickly serve interrupts , which allowed the machines to offer reasonable input/output performance with no added external hardware. To offer interrupts with similar performance as the 6502, the ARM design limited its physical address space to 64 MB of total addressable space, requiring 26 bits of address. As instructions were 4 bytes (32 bits) long, and required to be aligned on 4-byte boundaries,

7021-536: The US and worldwide markets during the 1980s and 1990s. Early in 1985, Gordon Moore decided to withdraw Intel from producing DRAM. By 1986, many, but not all, United States chip makers had stopped making DRAMs. Micron Technology and Texas Instruments continued to produce them commercially, and IBM produced them for internal use. In 1985, when 64K DRAM memory chips were the most common memory chips used in computers, and when more than 60 percent of those chips were produced by Japanese companies, semiconductor makers in

7140-540: The United States accused Japanese companies of export dumping for the purpose of driving makers in the United States out of the commodity memory chip business. Prices for the 64K product plummeted to as low as 35 cents apiece from $ 3.50 within 18 months, with disastrous financial consequences for some U.S. firms. On 4 December 1985 the US Commerce Department's International Trade Administration ruled in favor of

7259-654: The addition of simultaneous multithreading (SMT) for improved performance or fault tolerance . Acorn Computers ' first widely successful design was the BBC Micro , introduced in December 1981. This was a relatively conventional machine based on the MOS Technology 6502 CPU but ran at roughly double the performance of competing designs like the Apple II due to its use of faster dynamic random-access memory (DRAM). Typical DRAM of

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7378-640: The architecture, ARMv7, defines three architecture "profiles": Although the architecture profiles were first defined for ARMv7, ARM subsequently defined the ARMv6-M architecture (used by the Cortex M0 / M0+ / M1 ) as a subset of the ARMv7-M profile with fewer instructions. Except in the M-profile, the 32-bit ARM architecture specifies several CPU modes, depending on the implemented architecture features. At any moment in time,

7497-476: The bitline, which is almost always made of polysilicon, but is otherwise identical to the COB variation. The advantage the COB variant possesses is the ease of fabricating the contact between the bitline and the access transistor's source as it is physically close to the substrate surface. However, this requires the active area to be laid out at a 45-degree angle when viewed from above, which makes it difficult to ensure that

7616-415: The bitline. Sense amplifiers are required to read the state contained in the DRAM cells. When the access transistor is activated, the electrical charge in the capacitor is shared with the bitline. The bitline's capacitance is much greater than that of the capacitor (approximately ten times). Thus, the change in bitline voltage is minute. Sense amplifiers are required to resolve the voltage differential into

7735-436: The bitlines are divided into multiple segments, and the differential sense amplifiers are placed in between bitline segments. Because the sense amplifiers are placed between bitline segments, to route their outputs outside the array, an additional layer of interconnect placed above those used to construct the wordlines and bitlines is required. The DRAM cells that are on the edges of the array do not have adjacent segments. Since

7854-417: The capacitance can be increased by etching a deeper hole without any increase to surface area (Kenner, p. 44). Another advantage of the trench capacitor is that its structure is under the layers of metal interconnect, allowing them to be more easily made planar, which enables it to be integrated in a logic-optimized process technology, which have many levels of interconnect above the substrate. The fact that

7973-406: The capacitance, as well as the transistors that control access to it, is collectively referred to as a DRAM cell . They are the fundamental building block in DRAM arrays. Multiple DRAM memory cell variants exist, but the most commonly used variant in modern DRAMs is the one-transistor, one-capacitor (1T1C) cell. The transistor is used to admit current into the capacitor during writes, and to discharge

8092-410: The capacitor contact does not touch the bitline. CUB cells avoid this, but suffer from difficulties in inserting contacts in between bitlines, since the size of features this close to the surface are at or near the minimum feature size of the process technology (Kenner, pp. 33–42). The trench capacitor is constructed by etching a deep hole into the silicon substrate. The substrate volume surrounding

8211-417: The capacitor during reads. The access transistor is designed to maximize drive strength and minimize transistor-transistor leakage (Kenner, p. 34). The capacitor has two terminals, one of which is connected to its access transistor, and the other to either ground or V CC /2. In modern DRAMs, the latter case is more common, since it allows faster operation. In modern DRAMs, a voltage of +V CC /2 across

8330-405: The capacitor is required to store a logic one; and a voltage of −V CC /2 across the capacitor is required to store a logic zero. The resultant charge is Q = ± V C C 2 ⋅ C {\textstyle Q=\pm {V_{CC} \over 2}\cdot C} , where Q is the charge in coulombs and C is the capacitance in farads . Reading or writing

8449-410: The capacitor is under the logic means that it is constructed before the transistors are. This allows high-temperature processes to fabricate the capacitors, which would otherwise degrade the logic transistors and their performance. This makes trench capacitors suitable for constructing embedded DRAM (eDRAM) (Jacob, p. 357). Disadvantages of trench capacitors are difficulties in reliably constructing

8568-426: The capacitor to the write bitline just as in the 1T1C cell, but there was a separate read wordline and read transistor which connected an amplifier transistor to the read bitline. By the second generation, the drive to reduce cost by fitting the same amount of bits in a smaller area led to the almost universal adoption of the 1T1C DRAM cell, although a couple of devices with 4 and 16 Kbit capacities continued to use

8687-404: The capacitor's structures within deep holes and in connecting the capacitor to the access transistor's drain terminal (Kenner, p. 44). First-generation DRAM ICs (those with capacities of 1 Kbit), such as the archetypical Intel 1103 , used a three-transistor, one-capacitor (3T1C) DRAM cell with separate read and write circuitry. The write wordline drove a write transistor which connected

8806-479: The capacitors gradually leaks away; without intervention the data on the capacitor would soon be lost. To prevent this, DRAM requires an external memory refresh circuit which periodically rewrites the data in the capacitors, restoring them to their original charge. This refresh process is the defining characteristic of dynamic random-access memory, in contrast to static random-access memory (SRAM) which does not require data to be refreshed. Unlike flash memory , DRAM

8925-482: The column (the illustration to the right does not include this important detail). They are generally known as the + and − bit lines. A sense amplifier is essentially a pair of cross-connected inverters between the bit-lines. The first inverter is connected with input from the + bit-line and output to the − bit-line. The second inverter's input is from the − bit-line with output to the + bit-line. This results in positive feedback which stabilizes after one bit-line

9044-586: The commercialized Z-RAM from Innovative Silicon, the TTRAM from Renesas and the A-RAM from the UGR / CNRS consortium. DRAM cells are laid out in a regular rectangular, grid-like pattern to facilitate their control and access via wordlines and bitlines. The physical layout of the DRAM cells in an array is typically designed so that two adjacent DRAM cells in a column share a single bitline contact to reduce their area. DRAM cell area

9163-580: The complaint. Synchronous dynamic random-access memory (SDRAM) was developed by Samsung . The first commercial SDRAM chip was the Samsung KM48SL2000, which had a capacity of 16   Mb , and was introduced in 1992. The first commercial DDR SDRAM ( double data rate SDRAM) memory chip was Samsung's 64   Mb DDR SDRAM chip, released in 1998. Later, in 2001, Japanese DRAM makers accused Korean DRAM manufacturers of dumping. In 2002, US computer makers made claims of DRAM price fixing . DRAM

9282-494: The contemporary 1987 IBM PS/2 Model 50 , which initially utilised an Intel 80286 , offering 1.8 MIPS @ 10 MHz, and later in 1987, the 2 MIPS of the PS/2 70, with its Intel 386 DX @ 16 MHz. A successor, ARM3, was produced with a 4 KB cache, which further improved performance. The address bus was extended to 32 bits in the ARM6, but program code still had to lie within the first 64 MB of memory in 26-bit compatibility mode, due to

9401-400: The data consumes power, causing a variety of techniques to be used to manage the overall power consumption. For this reason, DRAM usually needs to operate with a memory controller ; the memory controller needs to know DRAM parameters, especially memory timings , to initialize DRAMs, which may be different depending on different DRAM manufacturers and part numbers. DRAM had a 47% increase in

9520-483: The design goal. They also considered the new 32-bit designs, but these cost even more and had the same issues with support chips. According to Sophie Wilson , all the processors tested at that time performed about the same, with about a 4 Mbit/s bandwidth. Two key events led Acorn down the path to ARM. One was the publication of a series of reports from the University of California, Berkeley , which suggested that

9639-412: The differential sense amplifiers require identical capacitance and bitline lengths from both segments, dummy bitline segments are provided. The advantage of the open bitline array is a smaller array area, although this advantage is slightly diminished by the dummy bitline segments. The disadvantage that caused the near disappearance of this architecture is the inherent vulnerability to noise , which affects

9758-524: The earlier 8-bit designs simply could not compete. Even newer 32-bit designs were also coming to market, such as the Motorola 68000 and National Semiconductor NS32016 . Acorn began considering how to compete in this market and produced a new paper design named the Acorn Business Computer . They set themselves the goal of producing a machine with ten times the performance of the BBC Micro, but at

9877-553: The effectiveness of the differential sense amplifiers. Since each bitline segment does not have any spatial relationship to the other, it is likely that noise would affect only one of the two bitline segments. The folded bitline array architecture routes bitlines in pairs throughout the array. The close proximity of the paired bitlines provide superior common-mode noise rejection characteristics over open bitline arrays. The folded bitline array architecture began appearing in DRAM ICs during

9996-450: The era ran at about 2 MHz; Acorn arranged a deal with Hitachi for a supply of faster 4 MHz parts. Machines of the era generally shared memory between the processor and the framebuffer , which allowed the processor to quickly update the contents of the screen without having to perform separate input/output (I/O). As the timing of the video display is exacting, the video hardware had to have priority access to that memory. Due to

10115-418: The forcing voltage is removed. During a write to a particular cell, all the columns in a row are sensed simultaneously just as during reading, so although only a single column's storage-cell capacitor charge is changed, the entire row is refreshed (written back in), as illustrated in the figure to the right. Typically, manufacturers specify that each row must be refreshed every 64 ms or less, as defined by

10234-512: The greatest density as well as allowing easier integration with high-performance logic circuits since they are constructed with the same SOI process technologies. Refreshing of cells remains necessary, but unlike with 1T1C DRAM, reads in 1T DRAM are non-destructive; the stored charge causes a detectable shift in the threshold voltage of the transistor. Performance-wise, access times are significantly better than capacitor-based DRAMs, but slightly worse than SRAM. There are several types of 1T DRAMs:

10353-485: The hole is then heavily doped to produce a buried n plate with low resistance. A layer of oxide-nitride-oxide dielectric is grown or deposited, and finally the hole is filled by depositing doped polysilicon, which forms the top plate of the capacitor. The top of the capacitor is connected to the access transistor's drain terminal via a polysilicon strap (Kenner, pp. 42–44). A trench capacitor's depth-to-width ratio in DRAMs of

10472-565: The interrupt itself. This meant FIQ requests did not have to save out their registers, further speeding interrupts. The first use of the ARM2 was the Acorn Archimedes personal computer models A305, A310, and A440 launched in 1987. According to the Dhrystone benchmark, the ARM2 was roughly seven times the performance of a typical 7 MHz 68000-based system like the Amiga or Macintosh SE . It

10591-449: The largest applications for DRAM is the main memory (colloquially called the RAM) in modern computers and graphics cards (where the main memory is called the graphics memory ). It is also used in many portable devices and video game consoles. In contrast, SRAM, which is faster and more expensive than DRAM, is typically used where speed is of greater concern than cost and size, such as

10710-425: The lengths of the bitlines and the number of attached DRAM cells attached to them are equal, two basic architectures to array design have emerged to provide for the requirements of the sense amplifiers: open and folded bitline arrays. The first generation (1 Kbit) DRAM ICs, up until the 64 Kbit generation (and some 256 Kbit generation devices) had open bitline array architectures. In these architectures,

10829-471: The levels specified by the logic signaling system. Modern DRAMs use differential sense amplifiers, and are accompanied by requirements as to how the DRAM arrays are constructed. Differential sense amplifiers work by driving their outputs to opposing extremes based on the relative voltages on pairs of bitlines. The sense amplifiers function effectively and efficient only if the capacitance and voltages of these bitline pairs are closely matched. Besides ensuring that

10948-421: The lower 2 bits of an instruction address were always zero. This meant the program counter (PC) only needed to be 24 bits, allowing it to be stored along with the eight bit processor flags in a single 32-bit register. That meant that upon receiving an interrupt, the entire machine state could be saved in a single operation, whereas had the PC been a full 32-bit value, it would require separate operations to store

11067-643: The lower price of the then-dominant magnetic-core memory. Capacitors had also been used for earlier memory schemes, such as the drum of the Atanasoff–Berry Computer , the Williams tube and the Selectron tube . In 1966, Dr. Robert Dennard invented modern DRAM architecture in which there's a single MOS transistor per capacitor, at the IBM Thomas J. Watson Research Center , while he was working on MOS memory and

11186-484: The market. 1981 was also the year that the IBM Personal Computer was introduced. Using the recently introduced Intel 8088 , a 16-bit CPU compared to the 6502's 8-bit design, it offered higher overall performance. Its introduction changed the desktop computer market radically: what had been largely a hobby and gaming market emerging over the prior five years began to change to a must-have business tool where

11305-402: The mid-1980s, beginning with the 256 Kbit generation. This architecture is favored in modern DRAM ICs for its superior noise immunity. This architecture is referred to as folded because it takes its basis from the open array architecture from the perspective of the circuit schematic. The folded array architecture appears to remove DRAM cells in alternate pairs (because two DRAM cells share

11424-407: The mid-2000s can exceed 50:1 (Jacob, p. 357). Trench capacitors have numerous advantages. Since the capacitor is buried in the bulk of the substrate instead of lying on its surface, the area it occupies can be minimized to what is required to connect it to the access transistor's drain terminal without decreasing the capacitor's size, and thus capacitance (Jacob, pp. 356–357). Alternatively,

11543-493: The number of register saves and restores performed in procedure calls ; the ARM design did not adopt this. Wilson developed the instruction set, writing a simulation of the processor in BBC ;BASIC that ran on a BBC Micro with a second 6502 processor . This convinced Acorn engineers they were on the right track. Wilson approached Acorn's CEO, Hermann Hauser , and requested more resources. Hauser gave his approval and assembled

11662-530: The price-per-bit in 2017, the largest jump in 30 years since the 45% jump in 1988, while in recent years the price has been going down. In 2018, a "key characteristic of the DRAM market is that there are currently only three major suppliers — Micron Technology , SK Hynix and Samsung Electronics " that are "keeping a pretty tight rein on their capacity". There is also Kioxia (previously Toshiba Memory Corporation after 2017 spin-off) which doesn't manufacture DRAM. Other manufacturers make and sell DIMMs (but not

11781-503: The reserved bits for the status flags. In the late 1980s, Apple Computer and VLSI Technology started working with Acorn on newer versions of the ARM core. In 1990, Acorn spun off the design team into a new company named Advanced RISC Machines Ltd., which became ARM Ltd. when its parent company, Arm Holdings plc, floated on the London Stock Exchange and Nasdaq in 1998. The new Apple–ARM work would eventually evolve into

11900-422: The row and column decoders (Jacob, pp. 358–361). Electrical or magnetic interference inside a computer system can cause a single bit of DRAM to spontaneously flip to the opposite state. The majority of one-off (" soft ") errors in DRAM chips occur as a result of background radiation , chiefly neutrons from cosmic ray secondaries, which may change the contents of one or more memory cells or interfere with

12019-495: The same price. This would outperform and underprice the PC. At the same time, the recent introduction of the Apple Lisa brought the graphical user interface (GUI) concept to a wider audience and suggested the future belonged to machines with a GUI. The Lisa, however, cost $ 9,995, as it was packed with support chips, large amounts of memory, and a hard disk drive , all very expensive then. The engineers then began studying all of

12138-506: The simpler design, compared with processors like the Intel 80286 and Motorola 68020 , some additional design features were used: ARM includes integer arithmetic operations for add, subtract, and multiply; some versions of the architecture also support divide operations. Dynamic random-access memory Dynamic random-access memory ( dynamic RAM or DRAM ) is a type of random-access semiconductor memory that stores each bit of data in

12257-498: The simulations on the ARM1 boards led to the late 1986 introduction of the ARM2 design running at 8 MHz, and the early 1987 speed-bumped version at 10 to 12 MHz. A significant change in the underlying architecture was the addition of a Booth multiplier , whereas formerly multiplication had to be carried out in software. Further, a new Fast Interrupt reQuest mode, FIQ for short, allowed registers 8 through 14 to be replaced as part of

12376-492: The single-transistor MOS DRAM memory cell. He filed a patent in 1967, and was granted U.S. patent number 3,387,286 in 1968. MOS memory offered higher performance, was cheaper, and consumed less power, than magnetic-core memory. The patent describes the invention: "Each cell is formed, in one embodiment, using a single field-effect transistor and a single capacitor." MOS DRAM chips were commercialized in 1969 by Advanced Memory Systems, Inc of Sunnyvale, CA . This 1024 bit chip

12495-399: The stacked capacitor, based on its location relative to the bitline—capacitor-under-bitline (CUB) and capacitor-over-bitline (COB). In the former, the capacitor is underneath the bitline, which is usually made of metal, and the bitline has a polysilicon contact that extends downwards to connect it to the access transistor's source terminal. In the latter, the capacitor is constructed above

12614-462: The substrate surface are referred to as trench capacitors. In the 2000s, manufacturers were sharply divided by the type of capacitor used in their DRAMs and the relative cost and long-term scalability of both designs have been the subject of extensive debate. The majority of DRAMs, from major manufactures such as Hynix , Micron Technology , Samsung Electronics use the stacked capacitor structure, whereas smaller manufacturers such Nanya Technology use

12733-536: The synthesizable RTL, the customer has the ability to perform architectural level optimisations and extensions. This allows the designer to achieve exotic design goals not otherwise possible with an unmodified netlist ( high clock speed , very low power consumption, instruction set extensions, etc.). While Arm Holdings does not grant the licensee the right to resell the ARM architecture itself, licensees may freely sell manufactured products such as chip devices, evaluation boards and complete systems. Merchant foundries can be

12852-453: The trench capacitor structure (Jacob, pp. 355–357). The capacitor in the stacked capacitor scheme is constructed above the surface of the substrate. The capacitor is constructed from an oxide-nitride-oxide (ONO) dielectric sandwiched in between two layers of polysilicon plates (the top plate is shared by all DRAM cells in an IC), and its shape can be a rectangle, a cylinder, or some other more complex shape. There are two basic variations of

12971-479: The wordline, is connected to the gate terminal of every access transistor in its row. The vertical bitline is connected to the source terminal of the transistors in its column. The lengths of the wordlines and bitlines are limited. The wordline length is limited by the desired performance of the array, since propagation time of the signal that must transverse the wordline is determined by the RC time constant . The bitline length

13090-449: The world's fastest supercomputer from 2020 to 2022. With over 230 billion ARM chips produced, since at least 2003, and with its dominance increasing every year , ARM is the most widely used family of instruction set architectures. There have been several generations of the ARM design. The original ARM1 used a 32-bit internal structure but had a 26-bit address space that limited it to 64 MB of main memory . This limitation

13209-508: Was as a second processor for the BBC Micro, where it helped in developing simulation software to finish development of the support chips (VIDC, IOC, MEMC), and sped up the CAD software used in ARM2 development. Wilson subsequently rewrote BBC BASIC in ARM assembly language . The in-depth knowledge gained from designing the instruction set enabled the code to be very dense, making ARM BBC BASIC an extremely good test for any ARM emulator. The result of

13328-431: Was generally described as "5-2-2-2" timing, as bursts of four reads within a page were common. When describing synchronous memory, timing is described by clock cycle counts separated by hyphens. These numbers represent t CL - t RCD - t RP - t RAS in multiples of the DRAM clock cycle time. Note that this is half of the data transfer rate when double data rate signaling is used. JEDEC standard PC3200 timing

13447-458: Was often found on workstations. The graphics system was also simplified based on the same set of underlying assumptions about memory and timing. The result was a dramatically simplified design, offering performance on par with expensive workstations but at a price point similar to contemporary desktops. The ARM2 featured a 32-bit data bus , 26-bit address space and 27 32-bit registers , of which 16 are accessible at any one time (including

13566-670: Was removed in the ARMv3 series, which has a 32-bit address space, and several additional generations up to ARMv7 remained 32-bit. Released in 2011, the ARMv8-A architecture added support for a 64-bit address space and 64-bit arithmetic with its new 32-bit fixed-length instruction set. Arm Holdings has also released a series of additional instruction sets for different rules; the "Thumb" extension adds both 32- and 16-bit instructions for improved code density , while Jazelle added instructions for directly handling Java bytecode . More recent changes include

13685-414: Was sold to Honeywell , Raytheon , Wang Laboratories , and others. The same year, Honeywell asked Intel to make a DRAM using a three-transistor cell that they had developed. This became the Intel 1102 in early 1970. However, the 1102 had many problems, prompting Intel to begin work on their own improved design, in secrecy to avoid conflict with Honeywell. This became the first commercially available DRAM,

13804-477: Was strongly motivated by economics, a major consideration for DRAM devices, especially commodity DRAMs. The minimization of DRAM cell area can produce a denser device and lower the cost per bit of storage. Starting in the mid-1980s, the capacitor was moved above or below the silicon substrate in order to meet these objectives. DRAM cells featuring capacitors above the substrate are referred to as stacked or folded plate capacitors. Those with capacitors buried beneath

13923-559: Was the most widely used architecture in mobile devices as of 2011 . Since 1995, various versions of the ARM Architecture Reference Manual (see § External links ) have been the primary source of documentation on the ARM processor architecture and instruction set, distinguishing interfaces that all ARM processors are required to support (such as instruction semantics) from implementation details that may vary. The architecture has evolved over time, and version seven of

14042-410: Was trying to create an alternative to SRAM which required six MOS transistors for each bit of data. While examining the characteristics of MOS technology, he found it was capable of building capacitors, and that storing a charge or no charge on the MOS capacitor could represent the 1 and 0 of a bit, while the MOS transistor could control writing the charge to the capacitor. This led to his development of

14161-488: Was twice as fast as an Intel 80386 running at 16 MHz, and about the same speed as a multi-processor VAX-11/784 superminicomputer . The only systems that beat it were the Sun SPARC and MIPS R2000 RISC-based workstations . Further, as the CPU was designed for high-speed I/O, it dispensed with many of the support chips seen in these machines; notably, it lacked any dedicated direct memory access (DMA) controller which

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