Universal memory refers to a

computer data storage Computer data storage is a technology consisting of computer components and Data storage, recording media that are used to retain digital data (computing), data. It is a core function and fundamental component of computers. The central pro ...

device combining the cost benefits of

DRAM Dynamic random-access memory (dynamic RAM or DRAM) 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-oxid ...

, the speed of SRAM, the non-volatility of

flash memory Flash memory is an electronic non-volatile computer memory storage medium that can be electrically erased and reprogrammed. The two main types of flash memory, NOR flash and NAND flash, are named for the NOR and NAND logic gates. Both us ...

along with infinite durability, and longevity. Such a device, if it ever becomes possible to develop, would have a far-reaching impact on the computer market. Some doubt that such a type of memory will ever be possible.

Computers A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These programs ...

, for most of their recent history, have depended on several different data storage technologies simultaneously as part of their operation. Each one operates at a level in the memory hierarchy where another would be unsuitable. A

personal computer A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tec ...

might include a few

megabytes The megabyte is a multiple of the unit byte for digital information. Its recommended unit symbol is MB. The unit prefix ''mega'' is a multiplier of (106) in the International System of Units (SI). Therefore, one megabyte is one million bytes o ...

of fast but volatile and expensive SRAM as the

CPU cache A CPU cache is a hardware cache used by the central processing unit (CPU) of a computer to reduce the average cost (time or energy) to access data from the main memory. A cache is a smaller, faster memory, located closer to a processor core, which ...

, several

gigabytes The gigabyte () is a multiple of the unit byte for digital information. The prefix '' giga'' means 109 in the International System of Units (SI). Therefore, one gigabyte is one billion bytes. The unit symbol for the gigabyte is GB. This definit ...

of slower

for program memory, and 128 GB-8 TB of the slow but non-volatile

or 1-10

terabyte The byte is a units of information, unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character (computing), character of text in a computer and for this ...

s of "spinning platters"

hard disk drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magnet ...

for long-term storage. For example, a university recommended students entering in 2015–2016 to have a PC with: ::- a CPU with a 4×256 KB L2 cache, and a 6 MB L3 cache ::- 16 GB DRAM ::- 256 GB

solid-state drive A solid-state drive (SSD) is a solid-state storage device that uses integrated circuit assemblies to store data persistently, typically using flash memory, and functioning as secondary storage in the hierarchy of computer storage. It is ...

, and ::- 1 TB hard disk drive Researchers seek to replace these different memory types with one single type to reduce the cost and increase performance. For a memory technology to be considered a universal memory, it would need to have best characteristics of several memory technologies. It would need to: ::- operate very quicklylike SRAM cache ::- support a practically unlimited number of read/write cycleslike SRAM and DRAM ::- retain data indefinitely without using powerlike flash memory and hard disk drives, and ::- be sufficiently large for common operating systems and application programs, yet affordablelike hard disk drives. The last criterion is likely to be satisfied last, as

economies of scale In microeconomics, economies of scale are the cost advantages that enterprises obtain due to their scale of operation, and are typically measured by the amount of output produced per unit of time. A decrease in cost per unit of output enables ...

in manufacturing reduce cost. Many types of memory technologies have been explored with the goal of creating a practical universal memory. These include: * low-voltage, non-volatile, compound-semiconductor memory (demonstrated) * magnetoresistive random-access memory (

MRAM Magnetoresistive random-access memory (MRAM) is a type of non-volatile random-access memory which stores data in magnetic domains. Developed in the mid-1980s, proponents have argued that magnetoresistive RAM will eventually surpass competing tec ...

) (in development and production) *

bubble memory Bubble memory is a type of non-volatile computer memory that uses a thin film of a magnetic material to hold small magnetized areas, known as ''bubbles'' or ''domains'', each storing one bit of data. The material is arranged to form a series o ...

(1970-1980, obsolete) *

racetrack memory Racetrack memory or domain-wall memory (DWM) is an experimental non-volatile memory device under development at IBM's Almaden Research Center by a team led by physicist Stuart Parkin. In early 2008, a 3-bit version was successfully demonstrated. ...

(currently experimental) * ferroelectric random-access memory (

FRAM Fram may refer to: Ships * ''Fram'' (ship), an arctic exploration vessel from Norway * MS ''Fram'', expedition cruise ship owned by Hurtigruten Group Places and geography * Fram, Paraguay, a town in Itapúa, Paraguay * Fram Formation, a se ...

) (in development and production) * phase-change memory ( PCM) * programmable metallization cell ( PMC) * resistive random-access memory (

RRAM Resistive random-access memory (ReRAM or RRAM) is a type of non-volatile (NV) random-access (RAM) computer memory that works by changing the resistance across a dielectric solid-state material, often referred to as a memristor. ReRAM bears some ...

) *

nano-RAM Nano-RAM is a proprietary computer memory technology from the company Nantero. It is a type of nonvolatile random-access memory based on the position of carbon nanotubes deposited on a chip-like substrate. In theory, the small size of the nanotub ...

memristor A memristor (; a portmanteau of ''memory resistor'') is a non-linear two-terminal electrical component relating electric charge and magnetic flux linkage. It was described and named in 1971 by Leon Chua, completing a theoretical quartet of fu ...

-based memory Since each memory has its limitations, none of these have yet reached the goals of universal memory.

References

{{Reflist Solid-state computer storage media Computer memory Non-volatile memory