Many game consoles use interchangeable ROM cartridges, allowing for one system to play multiple games. Shown here is the inside of a cartridge. The ROM is the IC on the right labeled "MX23C1603-12A".

Read-only memory

What is ROM full form? Read-only memory (ROM) could be a type of non-volatile memory utilized in computers and other electronic gadgets. Information put away in ROM cannot be electronically adjusted after the make of the memory gadget. Read-only memory is valuable for putting away computer program that's once in a while changed amid the life of the framework, moreover known as firmware. Program applications (like video diversions) for programmable gadgets can be conveyed as plug-in cartridges containing ROM.

About Computer program...

Strictly talking, read-only memory alludes to memory that's hard-wired, such as diode lattice or a cover ROM coordinates circuit (IC), which cannot be electronically[a] changed after make.In spite of the fact that discrete circuits can be modified in rule, through the expansion of bodge wires and/or the expulsion or substitution of components, ICs cannot. Adjustment of blunders, or overhauls to the program, require modern gadgets to be fabricated and to supplant the introduced device.

Floating-gate ROM semiconductor memory within the shape of erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM) and streak memory can be deleted and re-programmed. But ordinarily, this may as it were be done at moderately moderate speeds, may require extraordinary hardware to realize, and is regularly as it were conceivable a certain number of times.

The term "ROM" is in some cases utilized to allude to a ROM gadget containing particular computer program or a record with computer program to be put away in a writable ROM gadget.For case, clients adjusting or supplanting the Android working framework depict records containing a adjusted or substitution working framework as "custom ROMs" after the sort of capacity the record utilized to be composed to, and they may recognize between ROM (where computer program and information is put away, as a rule Streak memory) and Smash.

History

Discrete-component ROM

IBM utilized capacitor read-only capacity (CROS) and transformer read-only capacity (TROS) to store microcode for the littler System/360 models, the 360/85, and the starting two System/370 models (370/155 and 370/165). On a few models there was too a writeable control store (WCS) for extra diagnostics and imitating bolster. The Apollo Direction Computer utilized center rope memory, modified by threading wires through attractive cores.

Solid-state ROM

The easiest sort of solid-state ROM is as ancient as the semiconductor innovation itself. Combinational rationale doors can be joined physically to outline n-bit address input onto subjective values of m-bit information yield (a look-up table).With the innovation of the coordinates circuit came veil ROM. Veil ROM comprises of a network of word lines (the address input) and bit lines (the information yield), specifically joined with transistor switches, and can speak to an subjective look-up table with a customary physical format and unsurprising proliferation delay. Cover ROM is modified with photomasks in photolithography amid semiconductor fabricating. The cover characterizes physical highlights or structures that will be expelled, or included within the ROM chips, and the nearness or nonappearance of these highlights will speak to either a 1 or a bit, depending on the ROM design. In this way by plan, any endeavors to electronically alter the information will come up short, since the information is characterized by the nearness or nonappearance of physical highlights or structures that cannot be electronically changed.For each computer program program, indeed for modifications of the same program, the whole veil must be changed, which can be costly.

In cover ROM, the data is physically encoded within the circuit, so it can as it were be modified amid manufacture. This leads to a number of genuine disadvantages:

It is as it were prudent to purchase cover ROM in expansive amounts, since clients must contract with a foundry to deliver a custom plan for each piece, or amendment of software.
The turnaround time between completing the plan for a cover ROM and accepting the wrapped up item is long, for the same reason.
Mask ROM is illogical for R&D work since architects regularly got to rapidly adjust the substance of memory as they refine a plan.
If a item is transported with defective cover ROM, the as it were way to settle it is to review the item and physically supplant the ROM in each unit shipped.
Subsequent improvements have tended to these inadequacies. Programmable read-only memory (PROM), designed by Wen Tsing Chow in 1956, permitted clients to program its substance precisely once by physically changing its structure with the application of high-voltage beats. This tended to issues 1 and 2 over, since a company can basically arrange a expansive bunch of new PROM chips and program them with the required substance at its designers' convenience.

The appearance of the metal–oxide–semiconductor field-effect transistor (MOSFET), designed at Chime Labs in 1959, empowered the viable utilize of metal–oxide–semiconductor (MOS) transistors as memory cell capacity components in semiconductor memory, a work already served by attractive centers in computer memory. In 1967, Dawon Kahng and Simon Sze of Chime Labs proposed that the coasting entryway of a MOS semiconductor gadget can be utilized for the cell of a reprogrammable ROM, which driven to Dov Frohman of Intel designing erasable programmable read-only memory (EPROM) in 1971. The 1971 development of EPROM basically unraveled issue 3, since EPROM (not at all like PROM) can be more than once reset to its unprogrammed state by presentation to solid bright light.

Electrically erasable programmable read-only memory (EEPROM), created by Yasuo Tarui, Yutaka Hayashi and Kiyoko Naga at the Electrotechnical Research facility in 1972, went a long way to tackling issue 4, since an EEPROM can be modified in-place if the containing gadget gives a implies to get the program substance from an outside source (for illustration, a individual computer via a serial cable). Streak memory, invented by Fujio Masuoka at Toshiba within the early 1980s and commercialized within the late 1980s, may be a frame of EEPROM that creates very efficient utilize of chip region and can be eradicated and reconstructed thousands of times without harm. It licenses deletion and programming of as it were a particular portion of the gadget, rather than the whole gadget.This will be done at tall speed, thus the title "flash".

All of these advances made strides the adaptability of ROM, but at a noteworthy cost-per-chip, so that in expansive amounts veil ROM would stay an prudent choice for numerous a long time. (Diminishing fetched of reprogrammable gadgets had nearly dispensed with the showcase for cover ROM by the year 2000.) Rewriteable advances were imagined as substitutions for cover ROM.

The most later advancement is NAND streak, too concocted at Toshiba.Its architects expressly broke from past hone, expressing doubtlessly that "the point of NAND streak is to supplant difficult disks," instead of the conventional utilize of ROM as a frame of non-volatile essential capacity. As of 2021, NAND has about totally accomplished this objective by advertising throughput higher than difficult disks, lower inactivity, higher resistance of physical shock, extraordinary miniaturization (within the frame of USB streak drives and minor microSD memory cards, for illustration), and much lower power consumption.

Use for storing programs

Many stored-program computers use a shape of non-volatile capacity (that's , capacity that holds its information when control is evacuated) to store the beginning program that runs when the computer is fueled on or something else starts execution (a handle known as bootstrapping, regularly truncated to "booting" or "booting up"). Moreover, each non-trivial computer needs a few shape of changeable memory to record changes in its state because it executes.

Forms of read-only memory were utilized as non-volatile capacity for programs in most early stored-program computers, such as ENIAC after 1948. (Until at that point it was not a stored-program computer as each program had to be physically wired into the machine, which seem take days to weeks.) Read-only memory was less difficult to actualize since it required as it were a component to studied put away values, and not to alter them in-place, and hence may be actualized with exceptionally rough electromechanical gadgets (see historical cases underneath).With the approach of coordinates circuits within the 1960s, both ROM and its changeable partner inactive Smash were executed as clusters of transistors in silicon chips; in any case, a ROM memory cell might be actualized utilizing less transistors than an SRAM memory cell, since the last mentioned needs a lock (comprising 5-20 transistors) to hold its substance, whereas a ROM cell might comprise of the nonattendance (consistent 0) or nearness (coherent 1) of one transistor interfacing a bit line to a word line. Consequently, ROM may be executed at a lower cost-per-bit than Smash for numerous years.

Most domestic computers of the 1980s put away a Essential mediator or working framework in ROM as other shapes of non-volatile capacity such as attractive disk drives were as well exorbitant. For illustration, the Commodore 64 included 64 KB of Slam and 20 KB of ROM containing a Fundamental translator and the KERNAL working framework. Afterward domestic or office computers such as the IBM PC XT frequently included attractive disk drives, and bigger sums of Smash, permitting them to stack their working frameworks from disk into Slam, with as it were a minimal equipment initialization center and bootloader remaining in ROM (known as the BIOS in IBM-compatible computers).This course of action permitted for a more complex and effectively upgradeable working system.

In advanced PCs, "ROM" is utilized to store the essential bootstrapping firmware for the processor, as well as the different firmware required to inside control self-contained gadgets such as realistic cards, difficult disk drives, strong state drives, optical disc drives, TFT screens, etc., within the framework. Nowadays, numerous of these "read-only" recollections – particularly the BIOS/UEFI – are regularly supplanted with EEPROM or Streak memory (see underneath), to allow in-place reconstructing ought to the require for a firmware update emerge. Be that as it may, straightforward and develop sub-systems (such as the console or some communication controllers within the coordinates circuits on the most board, for illustration) may utilize cover ROM or OTP (one-time programmable).

ROM and successor advances such as streak are predominant in implanted frameworks. These are in everything from mechanical robots to domestic apparatuses and customer hardware (MP3 players, set-top boxes, etc.) all of which are planned for particular capacities, but are based on general-purpose chip. With program as a rule firmly coupled to equipment, program changes are once in a while required in such gadgets (which regularly need difficult disks for reasons of fetched, estimate, or control utilization). As of 2008, most items utilize Streak instead of veil ROM, and numerous give a few implies for interfacing to a PC for firmware upgrades; for case, a digital audio player may well be upgraded to bolster a modern record arrange.A few specialists have taken advantage of this adaptability to reconstruct shopper items for modern purposes; for case, the iPodLinux and OpenWrt ventures have empowered clients to run full-featured Linux conveyances on their MP3 players and remote switches, respectively.

ROM is additionally valuable for twofold storage of cryptographic information, because it makes them troublesome to supplant, which may be alluring in arrange to upgrade data security.

Use for putting away data

Since ROM (at slightest in hard-wired veil frame) cannot be adjusted, it is as it were reasonable for putting away information which isn't anticipated to require alteration for the life of the gadget. To that conclusion, ROM has been utilized in numerous computers to store look-up tables for the assessment of numerical and coherent capacities (for illustration, a floating-point unit might organize the sine work in arrange to encourage quicker computation). This was particularly viable when CPUs were moderate and ROM was cheap compared to Smash.

Notably, the show connectors of early individual computers put away tables of bitmapped text style characters in ROM. This ordinarily implied that the content show text style may not be changed intuitiveness. This was the case for both the CGA and MDA connectors accessible with the IBM PC XT.

The utilize of ROM to store such little sums of information has vanished nearly totally in present day general-purpose computers. In any case, NAND Streak has taken over a modern part as a medium for mass capacity or auxiliary capacity of records.

Types

Factory programmed

Mask ROM could be a read-only memory whose substance are programmed by the coordinates circuit manufacturer (instead of by the client). The required memory substance are outfitted by the customer to the gadget producer. The required information is changed over into a custom veil layer for the ultimate metallization of interconnects on the memory chip (subsequently the name).

The first EPRM, an Intel 1702, with the die and wire bonds clearly visible through the erase window.

Mask ROM can be made in a few ways, all of which point to change the electrical reaction of a transistor when it is tended to on a framework, such as:

In a ROM with transistors in a NOR arrangement, employing a photomask to characterize as it were particular zones of a lattice with transistors, to fill with metal hence interfacing to the grid only portion of all the transistors within the ROM chip hence making a network where transistors that are associated cause a diverse electrical reaction when tended to, than spaces within the network where the transistors are not associated, a associated transistor may speak to a 1 and an detached one a 0, or viceversa. Usually the least expensive, and speediest way of making cover ROM because it as it were needs one veil with information, and has the most reduced thickness of all cover ROM sorts because it is done at the metallization layer, whose features can be moderately expansive in regard to other parts of the ROM.This is often known as contact-programmed ROM. In ROM with a NAND setup, typically known as metal-layer programming and the cover characterizes where to fill the ranges encompassing transistors with metal which short-circuits the transistors instead, a transistor that's not brief circuited may speak to a 0, and one that's may speak to a 1, or viceversa.
Using two covers to characterize two sorts of particle implantation locales for transistors, to alter their electrical properties when tended to in a framework and characterize two sorts of transistors. The sort of transistor characterizes in the event that it speaks to a 1 or a bit. One veil characterizes where to store one sort of particle implantation (the "1" transistors), and another characterizes where to store the other (the "0" transistors).Typically known as voltage limit ROM (VTROM) as the diverse ion implantation sorts characterize diverse voltage limits within the transistors, and it's the voltage edge on a transistor that characterizes a 0, or a 1. Can be utilized with NAND and NOR arrangements. This procedure offers a tall level of resistance against optical perusing of the substance as ion-implantation districts are troublesome to recognize optically, which may be endeavored with decapping of the ROM and a microscope.
Using two levels of thickness for a entryway oxide in transistors, and employing a cover to characterize where to store one thickness of oxide, and another cover to store the other. Depending on the thickness a transistor can have diverse electrical properties and in this way speak to either a 1 or a 0.
Using a few covers to characterize the nearness or nonattendance of the transistors themselves, on a lattice. Tending to a non-existent transistor may be deciphered as a 0, and on the off chance that a transistor is display it may be deciphered as a 1, or viceversa. This can be known as active-layer programming.

Mask ROM transistors can be organized in either NOR or NAND arrangements and can accomplish one of the littlest cell sizes conceivable as each bit is spoken to by as it were one transistor. NAND offers higher capacity thickness than NOR.OR setups are too conceivable, but compared to NOR it as it were interfaces transistors to Vcc rather than Vss. Veil ROMs used to be the foremost cheap, and are the best semiconductor memory gadgets, with as it were one metal layer and one polysilicon layer, making it the sort of semiconductor memory with the most elevated fabricating yield (the most elevated number of working gadgets per fabricating run).

It is common hone to utilize rewritable non-volatile memory – such as UV-EPROM or EEPROM – for the improvement stage of a venture, and to switch to veil ROM when the code has been finalized. For illustration, Atmel microcontrollers come in both EEPROM and cover ROM formats.

The fundamental advantage of veil ROM is its fetched.Per bit, cover ROM is more compact than any other kind of semiconductor memory. Since the taken a toll of an coordinates circuit emphatically depends on its measure, cover ROM is altogether cheaper than any other kind of semiconductor memory.

However, the one-time veiling fetched is tall and there's a long turn-around time from plan to item stage. Plan blunders are expensive: if an mistake within the information or code is found, the veil ROM is futile and must be supplanted in arrange to alter the code or data.

As of 2003, four companies create most such veil ROM chips: Samsung Gadgets, NEC Organization, Oki Electric Industry, and Macronix.

Some coordinates circuits contain as it were veil ROM. Other coordinates circuits contain cover ROM as well as a assortment of other gadgets. In specific, numerous chip have cover ROM to store their microcode. A few microcontrollers have veil ROM to store the bootloader or all of their firmware.

Classic mask-programmed ROM chips are coordinates circuits that physically encode the information to be put away, and hence it is outlandish to alter their substance after manufacture.

It is additionally conceivable to compose the substance of a Laser ROM by employing a laser to change the electrical properties of only some diodes on the ROM, or by employing a laser to cut as it were a few polysilicon joins, rather than employing a mask.

Field programmable

Programmable read-only memory (PROM), or one-time programmable ROM (OTP), can be composed to or modified by means of a uncommon gadget called a PROM software engineer. Regularly, this gadget employments tall voltages to for all time devastate or make inner joins (wires or antifuses) inside the chip. Thus, a PROM can as it were be modified once.
Erasable programmable read-only memory (EPROM) can be eradicated by introduction to solid bright light (ordinarily for 10 minutes or longer), at that point revamped with a handle that once more needs higher than regular voltage connected.Rehashed presentation to UV light will inevitably wear out an EPROM, but the continuance of most EPROM chips surpasses 1000 cycles of deleting and reconstructing. EPROM chip bundles can regularly be distinguished by the unmistakable quartz "window" which permits UV light to enter. After programming, the window is regularly secured with a name to avoid coincidental eradication. A few EPROM chips are factory-erased some time recently they are bundled, and incorporate no window; these are successfully PROM.
Electrically erasable programmable read-only memory (EEPROM) is based on a comparative semiconductor structure to EPROM, but permits its whole substance (or chosen banks) to be electrically deleted, at that point revamped electrically, so that they require not be evacuated from the computer (whether general-purpose or an inserted computer in a camera, MP3 player, etc.). Composing or blazing an EEPROM is much slower (milliseconds per bit) than perusing from a ROM or composing to a Slam (nanoseconds in both cases).
Electrically alterable read-only memory (EAROM) may be a sort of EEPROM that can be modified one bit at a time. Composing could be a exceptionally moderate handle and once more needs higher voltage (ordinarily around 12 V) than is utilized for perused get to. EAROMs are expecting for applications that require occasional and as it were halfway modifying.EAROM may be utilized as non-volatile capacity for basic framework setup data; in numerous applications, EAROM has been supplanted by CMOS Smash provided by mains control and backed-up with a lithium battery.
Flash memory (or basically streak) could be a present day sort of EEPROM designed in 1984. Streak memory can be eradicated and revised speedier than conventional EEPROM, and more up to date plans include exceptionally tall perseverance (surpassing 1,000,000 cycles). Advanced NAND streak makes effective utilize of silicon chip region, coming about in person ICs with a capacity as tall as 32 GB as of 2007; this highlight, at the side its perseverance and physical toughness, has permitted NAND streak to supplant attractive in a few applications (such as USB
flash drives). NOR streak memory is some of the time called streak ROM or streak EEPROM when utilized as a substitution for more seasoned ROM sorts, but not in applications that take advantage of its capacity to be adjusted rapidly and regularly.

By applying compose assurance, a few sorts of reprogrammable ROMs may incidentally ended up read-only memory.

Other technologies

There are other sorts of non-volatile memory which are not based on solid-state IC technology, including:

Optical capacity media, such CD-ROM which is read-only (practically equivalent to to veiled ROM). CD-R is Type in Once Studied Numerous (closely resembling to PROM), whereas CD-RW underpins erase-rewrite cycles (closely resembling to EEPROM); both are outlined for backwards-compatibility with CD-ROM.
Diode lattice ROM, utilized in little sums in numerous computers within the 1960s as well as electronic work area calculators and console encoders for terminals. This ROM was modified by introducing discrete semiconductor diodes at chosen areas between a lattice of word line follows and bit line follows on a printed circuit board.
Resistor, capacitor, or transformer framework ROM, utilized in numerous computers until the 1970s.Like diode framework ROM, it was modified by putting components at chosen areas between a network of word lines and bit lines. ENIAC's Work Tables were resistor network ROM, modified by physically setting rotating switches. Different models of the IBM System/360 and complex fringe gadgets put away their microcode in either capacitor (called BCROS for adjusted capacitor read-only capacity on the 360/50 and 360/65, or CCROS for card capacitor read-only capacity on the 360/30) or
transformer (called TROS for transformer read-only capacity on the 360/20, 360/40 and others) network ROM.
Core rope, a frame of transformer network ROM innovation utilized where measure and weight were basic. This was utilized in NASA/MIT's Apollo Shuttle Computers, DEC's PDP-8 computers, the Hewlett-Packard 9100A calculator, and other places.This sort of ROM was modified by hand by weaving "word line wires" interior or exterior of ferrite transformer cores.
Diamond Ring stores, in which wires are strung through a arrangement of expansive ferrite rings that work as it were as detecting gadgets. These were utilized in TXE phone exchanges.

Transformer matrix ROM (TROS), from the IBM System 360/20

Speed

Although the relative speed of Slam vs. ROM has changed over time, as of 2007 expansive Smash chips can be studied quicker than most ROMs.For this reason (and to permit uniform get to), ROM substance is some of the time replicated to Smash or shadowed some time recently its to begin with utilize, and in this way studied from RAM.

Writing

For those sorts of ROM that can be electrically adjusted, composing speed has customarily been much slower than perusing speed, and it may require curiously tall voltage, the development of jumper plugs to apply write-enable signals, and uncommon lock/unlock command codes. Present day NAND Streak accomplishes the most noteworthy compose speeds of any rewritable ROM innovation, with speeds as tall as 10 GB/s. This has been empowered by the expanded speculation in both buyer and undertaking strong state drives and flash memory items for higher conclusion portable gadgets. On a specialized level the picks up have been accomplished by expanding parallelism both in controller plan and of capacity, the utilize of huge Measure read/write caches and the usage of memory cells which can store more than one bit (DLC, TLC and MLC).The last mentioned approach is more disappointment inclined but this has been to a great extent relieved by overprovisioning (the consideration of save capacity in a item which is obvious as it were to the drive controller) and by progressively advanced read/write calculations in drive firmware.

Endurance and data retention

Because they are composed by driving electrons through a layer of electrical cover onto a drifting transistor entryway, rewriteable ROMs can withstand as it were a restricted number of compose and eradicate cycles some time recently the separator is for all time harmed. Within the most punctual EPROMs, this might happen after as few as 1,000 type in cycles, whereas in present day Streak EEPROM the perseverance may surpass 1,000,000. The constrained continuance, as well as the higher taken a toll per bit, implies that Flash-based capacity is impossible to

completely supplant magnetic disk drives within the close future.

The timespan over which a ROM remains precisely clear isn't constrained by type in cycling.The information maintenance of EPROM, EAROM, EEPROM, and Streak may be time-limited by charge spilling from the drifting entryways of the memory cell transistors. Early era EEPROM's, within the mid-1980s by and large cited 5 or 6 year information maintenance. A review of EEPROM's advertised within the year 2020 appears producers citing 100 year information maintenance. Unfavorable situations will decrease the maintenance time (spillage is quickened by tall temperatures or radiation). Veiled ROM and fuse/antifuse PROM do not suffer from this effect, as their information maintenance depends on physical instead of electrical perpetual quality of the coordinates circuit, in spite of the fact that intertwine re-growth was once a issue in a few frameworks.

An EPROM

Content images

The substance of ROM chips can be extricated with extraordinary equipment gadgets and significant controlling program. This hone is common for, as a primary case, perusing the substance of more seasoned video amusement comfort cartridges. Another case is making reinforcements of firmware/OS ROMs from more seasoned computers or other gadgets - for authentic purposes, as in numerous cases, the first chips are PROMs and hence at chance of surpassing their usable information lifetime.

The resultant memory dump records are known as ROM pictures or shortened ROMs, and can be utilized to create copy ROMs - for case to deliver unused cartridges or as computerized records for playing in comfort emulators. The term ROM picture begun when most comfort diversions were disseminated on cartridges containing ROM chips, but accomplished such broad utilization that it is still connected to pictures of more current diversions disseminated on CD-ROMs or other optical media.

ROM pictures of commercial recreations, firmware, etc. more often than not contain copyrighted computer program. The unauthorized replicating and dissemination of copyrighted computer program may be a infringement of copyright laws in numerous wards, in spite of the fact that duplication for reinforcement purposes may be considered reasonable use depending on area. In any case, there's a flourishing community locked in within the dissemination and exchanging of such program and abandonware for preservation/sharing purposes.

Timeline

Date of introduction	Chip name	Capacity (bits)	ROM type	MOSFET	Manufacturer(s)	Process	Area
1956	?	?	PROM	?	Arma	?	?
1965	?	256 bit	ROM	Bipolar TTL	Sylvania	?	?
1965	?	1 kb	ROM	MOS	General Microelectronics	?	?
1969	3301	1 kb	ROM	Bipolar	Intel	?	?
1970	?	512 bit	PROM	Bipolar TTL	Radiation	?	?
1971	1702	2 kb	EPROM	Static MOS (silicon gate)	Intel	?	15 mm²
1974	?	4 kb	ROM	MOS	AMD, General Instrument	?	?
1974	?	?	EAROM	MNOS	General Instrument	?	?
1975	2708	8 kb	EPROM	NMOS (FGMOS)	Intel	?	?
1976	?	2 kb	EEPROM	MOS	Toshiba	?	?
1977	µCOM-43 (PMOS)	16 kb	PROM	PMOS	NEC	?	?
1977	2716	16 kb	EPROM	TTL	Intel	?	?
1978	EA8316F	16 kb	ROM	NMOS	Electronic Arrays	?	436 mm²
1978	µCOM-43 (CMOS)	16 kb	PROM	CMOS	NEC	?	?
1978	2732	32 kb	EPROM	NMOS (HMOS)	Intel	?	?
1978	2364	64 kb	ROM	NMOS	Intel	?	?
1980	?	16 kb	EEPROM	NMOS	Motorola	4,000 nm	?
1981	2764	64 kb	EPROM	NMOS (HMOS II)	Intel	3,500 nm	?
1982	?	32 kb	EEPROM	MOS	Motorola	?	?
1982	27128	128 kb	EPROM	NMOS (HMOS II)	Intel	?	?
1983	?	64 kb	EPROM	CMOS	Signetics	3,000 nm	?
1983	27256	256 kb	EPROM	NMOS (HMOS)	Intel	?	?
1983	?	256 kb	EPROM	CMOS	Fujitsu	?	?
January 1984	MBM 2764	64 kb	EEPROM	NMOS	Fujitsu	?	528 mm²
1984	?	512 kb	EPROM	NMOS	AMD	1,700 nm	?
1984	27512	512 kb	EPROM	NMOS (HMOS)	Intel	?	?
1984	?	1 Mb	EPROM	CMOS	NEC	1,200 nm	?
1987	?	4 Mb	EPROM	CMOS	Toshiba	800 nm	?
1990	?	16 Mb	EPROM	CMOS	NEC	600 nm	?
1993	?	8 Mb	MROM	CMOS	Hyundai	?	?
1995	?	1 Mb	EEPROM	CMOS	Hitachi	?	?
1995	?	16 Mb	MROM	CMOS	AKM, Hitachi	?	?