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95-571: The company was founded in June 1998 by Jeff Hawkins , Donna Dubinsky , and Ed Colligan , the original inventors of the PalmPilot and founders of Palm, Inc., after they became unhappy with the direction of the company after its acquisition by 3Com . Their Visor line of PDAs synced by USB , which was significantly faster than Palm's RS232 serial sync. The Springboard expansion slot provided GPS navigation, cameras, music players, cell phone service, and most of

190-696: A Bachelor of Science with a major in electrical engineering in 1979. His interest in pattern recognition for speech and text input to computers led him to enroll in the biophysics program at the University of California, Berkeley in 1986. While there he patented a "pattern classifier" for handwritten text, but his PhD proposal on developing a theory of the neocortex was rejected. Hawkins joined GRiD Systems in 1982, where he developed rapid application development (RAD) software called GRiDtask . As vice president of research from 1988 to 1992, he developed their pen-based computing initiative that in 1989 spawned

285-651: A Freescale DragonBall processor, a modified version of the OS from Palm that included an enhanced datebook, a city time graphical world clock, and an advanced calculator. Unlike the Palm Pilot, the Visor's IrDA port was placed on the side of the device to make room for the Springboard Expansion Slot . The Visor and Visor Deluxe weight is 5.4 oz. Their dimensions are 4.8 in × 3.0 in × 0.7 in. The display

380-651: A Palm, Inc. , product after Palm's acquisition of Handspring, as the PalmOne Treo 600. At the time, the GSM version of the phone was one of the few quad-band phones available in the United States. Jeff Hawkins Jeffrey Hawkins is an American businessman, computer scientist , neuroscientist and engineer. He co-founded Palm Computing — where he co-created the PalmPilot and Treo — and Handspring . He subsequently turned to work on neuroscience, founding in 2002

475-674: A 33-MHz Motorola DragonBall VZ processor while the Deluxe only supported a 16 or 20-MHz chip. More, the Visor Deluxe used OS 3.1H while the Visor Platinum used OS 3.5.2H. At the time of the release of the Platinum, it sported the fastest processor for a Palm OS device. Like all Visors, the Platinum contained a microphone, intended to be used for Springboard slot-based cell phones. Released in March 2001,

570-501: 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

665-466: 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

760-437: 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

855-412: 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

950-514: 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

1045-407: 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

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1140-523: A stake in, Hawkins founded the Redwood Neuroscience Institute in Menlo Park , California. In 2004, he co-authored On Intelligence with Sandra Blakeslee , laying out a theory on his " memory-prediction framework " of how the brain works. One of Hawkins' areas of interest is cortical columns . In 2016, he hypothesized that cortical columns did not capture just a sensation, but also

1235-462: 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

1330-444: 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

1425-450: 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,

1520-407: 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

1615-565: Is 2.25 inches square with diagonal span of 3.0 inches. When Handspring released the Visor Prism, it was flashlight-bright and the first Palm OS handheld to have a 16-bit color display (65,536 colors); the contemporary model (IIIc) produced by Palm only had an 8-bit color display (256 colors). Like Palm's IIIc, Prism's color screen turned nearly pitch black in sunlight. Prism's cobalt-blue-only case (and cradle, which required an attached AC charger, as USB cables could not supply sufficient power at

1710-466: Is a type of random-access semiconductor memory that stores each bit of data in 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

1805-442: 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

1900-439: 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

1995-413: 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

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2090-436: 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

2185-405: 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,

2280-424: 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

2375-408: 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

2470-489: 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

2565-443: 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

2660-537: The GRiDPad , one of the first tablet computers . Hawkins founded Palm Inc. , in January 1992. In 1998 he left the company along with Palm co-founders Donna Dubinsky and Ed Colligan to start Handspring . In March 2005, Hawkins, together with Dubinsky (Palm's original CEO) and Dileep George , founded Numenta, Inc. In 2002, after two decades of finding little interest from neuroscience institutions that he did not have

2755-497: 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

2850-468: 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

2945-490: 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,

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3040-461: The Redwood Neuroscience Institute . In 2005 he co-founded Numenta, where he leads a team in efforts to reverse-engineer the neocortex and enable machine intelligence technology based on brain theory. He is the co-author of On Intelligence (2004), which explains his memory-prediction framework theory of the brain, and the author of A Thousand Brains: A New Theory of Intelligence (2021). Hawkins attended Cornell University , where he received

3135-454: 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

3230-404: 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

3325-504: 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

3420-464: 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

3515-462: 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

3610-498: 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

3705-514: 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

3800-400: 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

3895-584: The Palm OS, version 3.5.2H3. Power came from two AAA batteries that would last up to two months. This model had a lower price, with which Handspring was hoping to attract new users. The display of all Visors measured 2.25 inches square with diagonal span of 3.0 inches. Released in September 2001, the Visor Pro was Handspring's last model in its Visor series of PDAs. The 4.8 in × 3.0 in × 0.7 in unit

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3990-544: The Treo line, with Handspring favoring slimmer designs that left no room for the large slots necessary to support Springboard cartridges; peripheral technologies such as SDIO would soon render the Springboard platform obsolete. Additionally, technological advances meant that much of the functionality provided by Springboard modules, such as additional memory, a camera, MP3 player , Wi-Fi antenna, and GPS, could now be integrated into

4085-536: 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

4180-484: 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

4275-702: The Visor Edge to access the Springboard Modules available. Released in September 2001, the Neo featured an MC68VZ328 DragonBall processor clocked at 33 MHz. It had 8 MB DRAM , an IrDA -compliant infrared interface, and Handspring's standard Springboard slot. Neo sported a 160×160-pixel, 4-bit grayscale (16 shades of gray) display. The 4.8 in × 3.0 in × 0.7 in unit, weighing in at 5.4 ounces, came in sleek, translucent Blue, Red, or Smoke-grey colored case. It used Handspring's modified version of

4370-455: The advances he and the Numenta team made in the development of their theory of how the brain understands the world and what it means to be intelligent. It also details how the "thousand brains" theory can affect machine intelligence, and how an understanding of the brain impacts the threats and opportunities facing humanity. It also offers a theory of what's missing in current AI. In 2003, Hawkins

4465-476: 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

4560-415: 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

4655-436: 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

4750-417: 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

4845-406: 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

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4940-410: 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

5035-417: 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

5130-405: 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

5225-410: 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

5320-426: 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

5415-404: 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

5510-482: 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

5605-586: 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

5700-580: 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

5795-400: 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

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5890-412: 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

5985-427: The display measuring the same as other Visors (2.25 inches square with diagonal span of 3.0 inches). The highest OS upgrade is OS 3.5.3. The Visor Platinum was similar to the Visor Deluxe. Apart from shell color, the exterior of the devices were indistinguishable. The Visor Platinum was available only in a silver (platinum) or black colored shell, as opposed to the Visor Deluxe's many color choices. The Platinum included

6080-553: 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

6175-418: 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

6270-579: The functions of a "smart phone". In June 2000, during the dot-com bubble , the company became a public company via an initial public offering . Shares rose 35% on the first day of trading. In 2003, the company merged with Palm, Inc.'s hardware division. Handspring first introduced the Visor Solo , which was black and contained 2 MB of onboard memory. The Visor Deluxe had the option of translucent colored models, and had 8 MB of onboard memory. The Visor and Visor Deluxe used Palm OS 3.1H running on

6365-512: 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:

6460-598: The handheld itself at reduced cost. The first models of the series, the Treo 180 and 180g were released in February 2002 as monochrome-screen GSM phones; the 180 had an integrated thumb keyboard , while the 180g had a Graffiti writing area in lieu of the keyboard. Handspring followed the Treo 180 with the Treo 90 in April 2002. The Treo 90 was the only Treo that was not a smartphone , as it did not have mobile telephony capabilities. At

6555-485: 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

6650-449: 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

6745-425: 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,

6840-471: 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

6935-643: 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

7030-402: 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

7125-407: 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,

7220-400: The name Treo . Except for the Treo 90 , all Treo devices were smartphones with integrated cellular phones, and nearly all featured built-in keyboards to enhance e-mail and SMS functionality. The Treo line met with success, attributed in large part to Handspring's in-house VisorPhone software, which was tightly integrated with the Palm OS. The Springboard feature was no longer available on

7315-530: 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

7410-401: The relative location of that sensation, in three dimensions rather than two ( situated capture ), in relation to what was around it. Hawkins explains, "When the brain builds a model of the world, everything has a location relative to everything else". In 2021, he published A Thousand Brains: A New Theory of Intelligence , a framework for intelligence and cortical computation. The book details

7505-422: 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

7600-492: 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

7695-435: The slim Visor Edge featured an MC68VZ328 DragonBall CPU clocked at 33 MHz. The 160×160-pixel, 4-bit grayscale (16 shades of gray) display was standard for most Palm PDAs. However, at the time it was the thinnest and lightest Visor, sizing in at 4.7 in × 3.1 in × 0.44 in and weighing 4.8 ounces with the display measuring the same 2.25 inches square with diagonal span of 3.0 inches as other Visors. It

7790-399: 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

7885-462: 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

7980-419: The time of release, it was the physically smallest Palm OS device on the market. The Treo 90 pioneered features such as a color screen and an SD card slot, which are found on all subsequent Treo models. The Treo 270 and Treo 300 were twin models; the former worked using GSM networks, while the latter was a CDMA phone, released by Sprint Corporation . The Treo 600 was the first Treo to be rebranded as

8075-557: The time) was a departure for a PDA line known for a broad array of colored cases. Prism's power came from a rechargeable lithium-ion battery , rather than two AAA batteries like previous Visors. However, despite the shoehorn-like contoured back to support the rechargeable battery, it did have the Visor Springboard slot ; the infrared port was again on the side. The Prism featured Palm OS 3.5.2H3, and weighed 6.9 oz. The dimensions were 4.8 in × 3.0 in × 0.8 in with

8170-453: 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

8265-561: The two values of a bit, conventionally called 0 and 1. The electric charge on 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

8360-479: 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

8455-673: Was elected as a member of the National Academy of Engineering "for the creation of the hand-held computing paradigm and the creation of the first commercially successful example of a hand-held computing device." He also served on the Advisory Board of the Secular Coalition for America where he has advised on the acceptance and inclusion of nontheism in American life. DRAM Dynamic random-access memory ( dynamic RAM or DRAM )

8550-431: 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

8645-447: Was packed with 8 MB RAM and Handspring's latest version of the Palm OS, version 3.5.2H. Available in three colors, Metallic Blue, Metallic Silver, and Metallic Red, it was also eye catching. The built-in rechargeable lithium-ion battery generally lasted two to four weeks on a charge. However, due to its size, the standard Springboard slot was accessed through a slide-on sleeve rather than a built-in slot. Nevertheless, this still allowed

8740-500: Was powered by an MC68VZ328 DragonBall processor clocked at 33 MHz. Weighing 5.7 ounces, the unit came with 16 MB RAM, a built-in microphone, and Handspring's Springboard slot. It had a 4-bit grayscale (16 grays), backlit, monochrome display. Its power supply came from a rechargeable lithium-ion battery. In early 2002, Handspring ceased production of the Visor line, replacing it with a line of handhelds that were to be more "communication-centric" in nature; these would be sold under

8835-462: 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,

8930-477: 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

9025-456: 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

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