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55-555: The hard disk used in the LifeDrive was selected by Palm for its fast spinup speed, but delays in application launching were inevitably longer than with flash-based handhelds. Many speed concerns were addressed with a user-applicable ROM update , which was released by Palm in December 2005. One of the first troubles for the Life Drive was when it was taken off of United Kingdom shelves because

110-632: A PC for firmware updates; for example, a digital audio player might be updated to support a new file format . Some hobbyists have taken advantage of this flexibility to reprogram consumer products for new purposes; for example, the iPodLinux and OpenWrt projects have enabled users to run full-featured Linux distributions on their MP3 players and wireless routers, respectively. ROM is also useful for binary storage of cryptographic data, as it makes them difficult to replace, which may be desirable in order to enhance information security . Since ROM (at least in hard-wired mask form) cannot be modified, it

165-504: A bit line to a word line. Consequently, ROM could be implemented at a lower cost-per- bit than RAM for many years. Most home computers of the 1980s stored a BASIC interpreter or operating system in ROM as other forms of non-volatile storage such as magnetic disk drives were too costly. For example, the Commodore 64 included 64 KB of RAM and 20 KB of ROM containing a BASIC interpreter and

220-524: A company can simply order a large batch of fresh PROM chips and program them with the desired contents at its designers' convenience. The advent of the metal–oxide–semiconductor field-effect transistor (MOSFET), invented at Bell Labs in 1959, enabled the practical use of metal–oxide–semiconductor (MOS) transistors as memory cell storage elements in semiconductor memory , a function previously served by magnetic cores in computer memory . In 1967, Dawon Kahng and Simon Sze of Bell Labs proposed that

275-538: A larger project that would be worked on by multiple IBM teams. In 1963, based on their experience with TROS, the Hursley team chose TROS to be implemented in the new IBM System/360 family of computers to run microcode . Card-capacitor read-only storage (CCROS) was also considered for the System/360, with both TROS and CCROS being developed for the System/360. Due to unexpectedly high amounts of electrical noise from CCROS,

330-411: A new role as a medium for mass storage or secondary storage of files. Mask ROM is a read-only memory whose contents are programmed by the integrated circuit manufacturer (rather than by the user). The desired memory contents are furnished by the customer to the device manufacturer. The desired data is converted into a custom photomask /mask layer for the final metallization of interconnections on

385-411: A pulse of electricity would pass through one of the word lines. Whenever a current passes through a transformer core, a current is induced into the sense winding. A separate system (such as a gas tube) would detect this current in the sense winding and register a 1 . Subsequently, a 0 would be registered if no current was detected. The earliest form of TROS was developed by T. L. Dimond in 1945 for

440-536: A sense winding, would wrap around one part of the transformer core. The first version of TROS used large permalloy cores as magnetic cores. The permalloy cores would be placed side by side, with the hole of the core facing upwards for word lines to go through. Magnet wire was used as word lines for this version of TROS. The sense winding would connect to a gas tube. Later designs for the IBM System/360 had removable sheets of Mylar with embedded copper wiring as

495-511: A specific part of the device, instead of the entire device. This can be done at high speed, hence the name "flash". All of these technologies improved the flexibility of ROM, but at a significant cost-per-chip, so that in large quantities mask ROM would remain an economical choice for many years. (Decreasing cost of reprogrammable devices had almost eliminated the market for mask ROM by the year 2000.) Rewriteable technologies were envisioned as replacements for mask ROM. The most recent development

550-416: A technical level the gains have been achieved by increasing parallelism both in controller design and of storage, the use of large DRAM read/write caches and the implementation of memory cells which can store more than one bit (DLC, TLC and MLC). The latter approach is more failure prone but this has been largely mitigated by overprovisioning (the inclusion of spare capacity in a product which is visible only to

605-504: A three-position power switch (on, off, keylock), and a dedicated screen rotation button. The new power switch became a feature of the Treo smartphone line; the screen rotation button also appeared on the TX , but was later phased out among Palm devices, with dedicated accelerometers taking over the task of properly orienting the screen. The ROM update for the LifeDrive is available at palm.com . It

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660-406: A variety of other devices. In particular, many microprocessors have mask ROM to store their microcode . Some microcontrollers have mask ROM to store the bootloader or all of their firmware . Classic mask-programmed ROM chips are integrated circuits that physically encode the data to be stored, and thus it is impossible to change their contents after fabrication. It is also possible to write

715-436: Is NAND flash , also invented at Toshiba. Its designers explicitly broke from past practice, stating plainly that "the aim of NAND flash is to replace hard disks ," rather than the traditional use of ROM as a form of non-volatile primary storage . As of 2021 , NAND has nearly completely achieved this goal by offering throughput higher than hard disks, lower latency, higher tolerance of physical shock, extreme miniaturization (in

770-495: Is a thriving community engaged in the distribution and trading of such software for preservation/sharing purposes. Transformer read-only storage Transformer read-only storage (TROS) was a type of read-only memory (ROM) used between the mid-1940s to the late 1960s, prior to the common use of semiconductor ROM . TROS consisted of wires fed through and around transformer cores. The wires would register binary digits (1s and 0s) through inductance and separate wires sensing

825-407: Is common practice to use rewritable non-volatile memory – such as UV- EPROM or EEPROM – for the development phase of a project, and to switch to mask ROM when the code has been finalized. For example, Atmel microcontrollers come in both EEPROM and mask ROM formats. The main advantage of mask ROM is its cost. Per bit, mask ROM was more compact than any other kind of semiconductor memory . Since

880-413: Is only suitable for storing data which is not expected to need modification for the life of the device. To that end, ROM has been used in many computers to store look-up tables for the evaluation of mathematical and logical functions (for example, a floating-point unit might tabulate the sine function in order to facilitate faster computation). This was especially effective when CPUs were slow and ROM

935-525: Is possible to replace the stock 4 GB Microdrive with a 4GB Compact Flash card, improving battery life and operating speed due to the lower power consumption of flash memory and relative speed increased compared to hard disks. Left side: Voice Memo, Screen rotation Front: Home, Media, Files, Star, 5-way navigator Read-only memory Read-only memory ( ROM ) is a type of non-volatile memory used in computers and other electronic devices . Data stored in ROM cannot be electronically modified after

990-415: Is still applied to images of newer games distributed on CD-ROMs or other optical media. ROM images of commercial games, firmware, etc. usually contain copyrighted software. The unauthorized copying and distribution of copyrighted software is a violation of copyright laws in many jurisdictions, although duplication for backup purposes may be considered fair use depending on location. In any case, there

1045-452: Is stored, usually Flash memory ) and RAM. ROM and RAM are essential components of a computer, each serving distinct roles. RAM, or Random Access Memory, is a temporary, volatile storage medium that loses data when the system powers down. In contrast, ROM, being non-volatile, preserves its data even after the computer is switched off. IBM used capacitor read-only storage (CROS) and transformer read-only storage (TROS) to store microcode for

1100-536: Is typically only possible a certain number of times. The term "ROM" is sometimes used to refer to a ROM device containing specific software or a file with software to be stored in a writable ROM device. For example, users modifying or replacing the Android operating system describe files containing a modified or replacement operating system as " custom ROMs " after the type of storage the file used to be written to, and they may distinguish between ROM (where software and data

1155-507: Is used to store the basic bootstrapping firmware for the processor, as well as the various firmware needed to internally control self-contained devices such as graphic cards , hard disk drives , solid-state drives , optical disc drives , TFT screens , etc., in the system. Today, many of these "read-only" memories – especially the BIOS / UEFI – are often replaced with EEPROM or Flash memory (see below), to permit in-place reprogramming should

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1210-640: The Electrotechnical Laboratory in 1972, went a long way to solving problem 4, since an EEPROM can be programmed in-place if the containing device provides a means to receive the program contents from an external source (for example, a personal computer via a serial cable ). Flash memory , invented by Fujio Masuoka at Toshiba in the early 1980s and commercialized in the late 1980s, is a form of EEPROM that makes very efficient use of chip area and can be erased and reprogrammed thousands of times without damage. It permits erasure and programming of only

1265-616: The KERNAL operating system. Later home or office computers such as the IBM PC XT often included magnetic disk drives, and larger amounts of RAM, allowing them to load their operating systems from disk into RAM, with only a minimal hardware initialization core and bootloader remaining in ROM (known as the BIOS in IBM-compatible computers). This arrangement allowed for a more complex and easily upgradeable operating system. In modern PCs, "ROM"

1320-512: The floating gate of a MOS semiconductor device could be used for the cell of a reprogrammable ROM, which led to Dov Frohman of Intel inventing erasable programmable read-only memory (EPROM) in 1971. The 1971 invention of EPROM essentially solved problem 3, since EPROM (unlike PROM) can be repeatedly reset to its unprogrammed state by exposure to strong ultraviolet light. Electrically erasable programmable read-only memory (EEPROM), developed by Yasuo Tarui, Yutaka Hayashi and Kiyoko Naga at

1375-418: The 1960s, both ROM and its mutable counterpart static RAM were implemented as arrays of transistors in silicon chips; however, a ROM memory cell could be implemented using fewer transistors than an SRAM memory cell, since the latter needs a latch (comprising 5-20 transistors) to retain its contents, while a ROM cell might consist of the absence (logical 0) or presence (logical 1) of one transistor connecting

1430-539: The Hursley team chose TROS to be used for the Model 20 and Model 40, with CCROS implemented in the Model 30 . This version of TROS had sheets of Mylar with copper wiring, making manufacturing and code adjustments easier. Larger models of the System/360 would alternatively use the faster balanced-capacitor read-only storage (BCROS) to accommodate the desired higher performance. By the late 1960s, semiconductor memory had gotten cheaper,

1485-770: The No. 5 Crossbar switch. Within Bell Laboratories, TROS was called the Dimond ring translator. Its purpose was to convert an equipment number to a directory number for the AMA equipment in the Crossbar switch, which billed phone calls. In 1959, TROS was used in the Scientific Computer and Modular Processor (SCAMP) project by the IBM Hursley team . The SCAMP project would be scrapped in favor of

1540-466: The ROM chips, and the presence or absence of these features will represent either a 1 or a 0 bit, depending on the ROM design. Thus by design, any attempts to electronically change the data will fail, since the data is defined by the presence or absence of physical features or structures that cannot be electronically changed. For every software program, even for revisions of the same program, the entire mask must be changed, which can be costly. In mask ROM,

1595-546: The addition of bodge wires and the removal or replacement of components, ICs cannot. Correction of errors, or updates to the software, require new devices to be manufactured and to replace the installed device. Floating-gate ROM semiconductor memory in the form of erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM) and flash memory can be erased and re-programmed. But usually, this can only be done at relatively slow speeds, may require special equipment to achieve, and

1650-656: The change in current. Transformer read-only storages were first invented by T. L. Dimond in 1945 at Bell Laboratories for the No. 5 Crossbar switch to assist in the automatic message accounting (AMA) equipment. Later applications include the Bell Laboratories Model 6 computer and the IBM System/360 Model 20 and Model 40 . TROS was considered simple in design, albeit with flaws that discouraged later applications due to demands for higher computer performance. TROS

1705-423: The contents of a Laser ROM by using a laser to alter the electrical properties of only some diodes on the ROM, or by using a laser to cut only some polysilicon links, instead of using a mask. By applying write protection , some types of reprogrammable ROMs may temporarily become read-only memory. There are other types of non-volatile memory which are not based on solid-state IC technology, including: Although

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1760-453: The contents of the microcode memory. TROS was known to be slower than other forms of read-only memory around the 1960s. TROS had a cycle time of 600 nanoseconds and an access time of 240 nanoseconds on a 10 bit storage. BCROS, although smaller in memory size, had a cycle time of 200 nanoseconds and an access time of 90 nanoseconds. CCROS had an access time of 10 microseconds for 10 bit storage and 100 nanoseconds for 10 bit storage. TROS

1815-660: The cost of an integrated circuit strongly depends on its size, mask ROM is significantly cheaper than any other kind of semiconductor memory. However, the one-time masking cost is high and there is a long turn-around time from design to product phase. Design errors are costly: if an error in the data or code is found, the mask ROM is useless and must be replaced in order to change the code or data. As of 2003 , four companies produce most such mask ROM chips: Samsung Electronics , NEC Corporation , Oki Electric Industry , and Macronix . Some integrated circuits contain only mask ROM. Other integrated circuits contain mask ROM as well as

1870-463: The data is physically encoded in the circuit, so it can only be programmed during fabrication. This leads to a number of serious disadvantages: Subsequent developments have addressed these shortcomings. Programmable read-only memory (PROM), invented by Wen Tsing Chow in 1956, allowed users to program its contents exactly once by physically altering its structure with the application of high-voltage pulses. This addressed problems 1 and 2 above, since

1925-453: The device fell short of EU regulations on the use of hazardous materials. Finally, due to its high price, slower performance than other handhelds, and advances in flash memory which led to reduced prices and greater capacities, the LifeDrive did not fare well in the market, and was discontinued on January 31, 2007. Besides being the first Palm device with a hard drive, the LifeDrive introduced other features that were new to Palm devices, such as

1980-453: The drive controller) and by increasingly sophisticated read/write algorithms in drive firmware. Because they are written by forcing electrons through a layer of electrical insulation onto a floating transistor gate , rewriteable ROMs can withstand only a limited number of write and erase cycles before the insulation is permanently damaged. In the earliest EPROMs, this might occur after as few as 1,000 write cycles, while in modern Flash EEPROM

2035-418: The endurance may exceed 1,000,000. The limited endurance, as well as the higher cost per bit, means that Flash-based storage is unlikely to completely supplant magnetic disk drives in the near future. The timespan over which a ROM remains accurately readable is not limited by write cycling. The data retention of EPROM, EAROM, EEPROM, and Flash may be time-limited by charge leaking from the floating gates of

2090-721: The form of USB flash drives and tiny microSD memory cards , for example), and much lower power consumption. Many stored-program computers use a form of non-volatile storage (that is, storage that retains its data when power is removed) to store the initial program that runs when the computer is powered on or otherwise begins execution (a process known as bootstrapping , often abbreviated to " booting " or "booting up"). Likewise, every non-trivial computer needs some form of mutable memory to record changes in its state as it executes. Forms of read-only memory were employed as non-volatile storage for programs in most early stored-program computers, such as ENIAC after 1948 . (Until then it

2145-442: The integrated circuit, although fuse re-growth was once a problem in some systems. The contents of ROM chips can be extracted with special hardware devices and relevant controlling software. This practice is common for, as a main example, reading the contents of older video game console cartridges . Another example is making backups of firmware/OS ROMs from older computers or other devices - for archival purposes, as in many cases,

2200-499: The invention of the integrated circuit came mask ROM . Mask ROM consists of a grid of word lines (the address input) and bit lines (the data output), selectively joined with transistor switches, and can represent an arbitrary look-up table with a regular physical layout and predictable propagation delay . Mask ROM is programmed with photomasks in photolithography during semiconductor manufacturing . The mask defines physical features or structures that will be removed, or added in

2255-555: The manufacture of the memory device . Read-only memory is useful for storing software that is rarely changed during the life of the system, also known as firmware . Software applications, such as video games , for programmable devices can be distributed as plug-in cartridges containing ROM . Strictly speaking, read-only memory refers to hard-wired memory, such as diode matrix or a mask ROM integrated circuit (IC), that cannot be electronically changed after manufacture. Although discrete circuits can be altered in principle, through

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2310-475: The memory cell transistors. Early generation EEPROM's, in the mid-1980s generally cited 5 or 6 year data retention. A review of EEPROM's offered in the year 2020 shows manufacturers citing 100 year data retention. Adverse environments will reduce the retention time (leakage is accelerated by high temperatures or radiation ). Masked ROM and fuse/antifuse PROM do not suffer from this effect, as their data retention depends on physical rather than electrical permanence of

2365-548: The memory chip (hence the name). Mask ROM can be made in several ways, all of which aim to change the electrical response of a transistor when it is addressed on a grid, such as: Mask ROM transistors can be arranged in either NOR or NAND configurations and can achieve one of the smallest cell sizes possible as each bit is represented by only one transistor. NAND offers higher storage density than NOR. OR configurations are also possible, but compared to NOR it only connects transistors to V cc instead of V ss . Mask ROMs used to be

2420-417: The most inexpensive, and are the simplest semiconductor memory devices, with only one metal layer and one polysilicon layer, making it the type of semiconductor memory with the highest manufacturing yield (the highest number of working devices per manufacturing run). ROM can be made using one of several semiconductor device fabrication technologies such as CMOS , nMOS , pMOS , and bipolar transistors . It

2475-405: The movement of jumper plugs to apply write-enable signals, and special lock/unlock command codes. Modern NAND Flash can be used to achieve the highest write speeds of any rewritable ROM technology, with speeds as high as 10 GB / s in an SSD. This has been enabled by the increased investment in both consumer and enterprise solid-state drives and flash memory products for higher end mobile devices. On

2530-858: The need for a firmware upgrade arise. However, simple and mature sub-systems (such as the keyboard or some communication controllers in the integrated circuits on the main board, for example) may employ mask ROM or OTP (one-time programmable). ROM and successor technologies such as flash are prevalent in embedded systems . These are in everything from industrial robots to home appliances and consumer electronics ( MP3 players , set-top boxes , etc.) all of which are designed for specific functions, but are based on general-purpose microprocessors . With software usually tightly coupled to hardware, program changes are rarely needed in such devices (which typically lack hard disks for reasons of cost, size, or power consumption). As of 2008, most products use Flash rather than mask ROM, and many provide some means for connecting to

2585-459: The original chips are PROMs and thus at risk of exceeding their usable data lifetime. The resultant memory dump files are known as ROM images or abbreviated ROMs , and can be used to produce duplicate ROMs - for example to produce new cartridges or as digital files for playing in console emulators . The term ROM image originated when most console games were distributed on cartridges containing ROM chips, but achieved such widespread usage that it

2640-443: The relative speed of RAM vs. ROM has varied over time, as of 2007 large RAM chips can be read faster than most ROMs. For this reason (and to allow uniform access), ROM content is sometimes copied to RAM or shadowed before its first use, and subsequently read from RAM. For those types of ROM that can be electrically modified, writing speed has traditionally been much slower than reading speed, and it may need unusually high voltage,

2695-583: The smaller System/360 models, the 360/85 , and the initial two System/370 models ( 370/155 and 370/165 ). On some models there was also a writeable control store (WCS) for additional diagnostics and emulation support. The Apollo Guidance Computer used core rope memory , programmed by threading wires through magnetic cores. The simplest type of solid-state ROM is as old as the semiconductor technology itself. Combinational logic gates can be joined manually to map n -bit address input onto arbitrary values of m -bit data output (a look-up table ). With

2750-479: The word lines. These sheets would surround a transformer core consisting of a U-shaped and I-shaped ferrite core. The copper wiring would be arranged in a grid-like pattern, with some lines disconnected to allow the current to pass through or around a core. The sense windings would wind around the I-shaped section of the ferrite core, with the sense windings connected to output connections. To retrieve memory from TROS,

2805-464: Was also difficult to alter once word lines were threaded. Typically, word lines that needed to be changed were disconnected and left in the system, while a new wire was threaded. This limitation was overcome with the use of Mylar sheets, allowing for easy removal and installation of new word lines. In some cases, output signals could be registered without the word line threading through a transformer. Word lines placed too close to one another would create

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2860-567: Was cheap compared to RAM. Notably, the display adapters of early personal computers stored tables of bitmapped font characters in ROM. This usually meant that the text display font could not be changed interactively. This was the case for both the CGA and MDA adapters available with the IBM PC XT. The use of ROM to store such small amounts of data has disappeared almost completely in modern general-purpose computers. However, NAND Flash has taken over

2915-646: Was created by IBM as a read-only storage method for storing microcode for IBM computers. TROS used stacks of removable Mylar flexible printed wiring sheets that fitted onto fixed transformer bases. It was used on the IBM System/360 Model 20 , IBM System/360 Model 40 and the Type 2841 file control unit. The design of TROS is based on induced current from wires passing through magnetic ring-shaped transformer cores. Wires, called word lines, are threaded through and out of these ring-shaped cores. Another wire, called

2970-401: Was easier to store, and could hold more memory than TROS, rendering TROS obsolete. TROS memory was used to store microcode for mainframe computers and intelligent controllers used to control sophisticated storage devices such as disk drives and tape drives. If there were a bug in the microcode it was possible to rework it by replacing one or more of the printed wiring sheets, thereby changing

3025-408: Was not a stored-program computer as every program had to be manually wired into the machine, which could take days to weeks.) Read-only memory was simpler to implement since it needed only a mechanism to read stored values, and not to change them in-place, and thus could be implemented with very crude electromechanical devices (see historical examples below). With the advent of integrated circuits in

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