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Memory is the ability to store, retain, and recall information and experiences as researched in cognitive science. Computer memory refers to physical devices used to store data and sequences of instructions (programs) on a temporary or permanent basis, typically distinguished as fast random-access memory and relatively slow data storage.
RNA, biological data storage [1]


A flip-flop or latch is a one bit memory. For instance a simple relay (K1) with its contact parallel to the On-push-button S2, "remembers" whether last action was pushing S1 (reset) or S2 (set) [2] .
A RS flip-flop is a pair of cross-coupled NAND or NOR-gates, where the outputs are feed back to the inputs. A D flip-flop, the most common flip-flop, stores the input D with the rising edge (0-1 transition) of a clock.
RS flip-flop
D flip-flop
from two NOR (red == 1) [3]
from six NAND [4]
PDP-6 flip-flop [5] [6]

N-Bit Latches

N-Bit latches are arrays of one-bit latches or flip-flops typically as wide as a connected parallel data-bus. They may be used as a registers or scratchpad RAM inside a central processing unit.


Random access memory is a fast form of computer memory and refers to the idea that any piece of data can be stored and retrieved in a constant time, regardless of its physical location and whether or not it is related to the previous piece of data.

Static RAM

Static RAM (SRAM) is an array of latches, where each latch has a unique address, which connects the addressed latch to its data-bus, often used as CPU cache.

Dynamic RAM

Dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor within an electronic circuit. Since capacitors leak charge, the information eventually fades unless the capacitor charge is refreshed periodically, which is the reason to call that memory dynamic. Since DRAM takes only one transistor and capacitor per bit, it is therefor used as cheap main memory part of recent computer data storage, despite its worse latency compared to SRAM.

DRAM write at a 4 by 4 array [7]


Read-only memory (ROM) is a class of storage programmed once and mainly used to distribute firmware. EPROMs have a small quartz window which admits UV light for erasure [8] . ROM or EPROM were often embedded inside a microcontroller in conjunction with some RAM. They were often used in dedicated chess computers.


Since each data-bit stored in a ROM is a boolean function of its inputs or address, a ROM is also used to implement combinatorial logic.

Auxiliary Storage

Beside the computer's random access main memory, auxiliary storage refer to mass storage like optical discs, and magnetic storage hard disk drives. Those devices are usually connected via a serial bus, and accessed via streams.

Compact Cassette as Auxiliary Storage in Intelligent Chess [10]

Historical Data Storage

Memory Hierarchy

  • ComputerMemoryHierarchy.svg.png

Memory Management

Todays processors utilize all the above types of memory from small and fast to large but slow within the concepts of virtual memory, paging, protection and various caches.

Virtual Memory


Physical address translation [12]

Virtual and physical address space [13]



Huge Pages

Note that what Windows calls "large pages," Linux and Unix call "huge pages" or "huge TLB pages (x86 and x86-64)

Memory Model

Shared Memory




Memory Footprint

Beside their individual memory footprint, chess programs have to deal with huge memory areas of transposition table and possibly caches for endgame table- or bitbases and their relative huge random access latencies.


Memory versus Search

See also


Computer Memory

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  • Adriaan de Groot (1966). Perception and Memory versus Thought: Some Old Ideas and Recent Findings. Problem Solving: Research, Method, and Theory (ed. B. Kleinmuntz), pp. 19-50. John Wiley, New York.

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External Links

Computer Memory

Gustavo Duarte's Blog

from Best Of by Gustavo Duarte:





  1. ^ Data storage device from Wikipedia
  2. ^ Selbsthaltefunktion from Wikidepia.de (German)
  3. ^ Latch (electronics) from Wikipedia
  4. ^ Flip-flop (electronics) from Wikipedia
  5. ^ Bits by Lawrence J. Krakauer
  6. ^ PDP-6 Circuit Instruction Manual, © 1966, Digital Equipment Corporation (pdf)
  7. ^ Dynamic random access memory from Wikipedia
  8. ^ How to program a 2716
  9. ^ EPROM from Schachcomputer.info Wiki (German)
  10. ^ Intelligent Chess from Chess Computer UK by Mike Watters
  11. ^ 3D XPoint by Edmund Moshammer, CCC, August 02, 2015
  12. ^ Page table from Wikipedia
  13. ^ Virtual address from Wikipedia
  14. ^ Cache-oblivious algorithm from Wikipedia
  15. ^ DNA data storage breaks records : Nature News & Comment by Monya Baker, August 16, 2012
  16. ^ DNA data storage breaks records by Terry McCracken, CCC, August 18, 2012
  17. ^ K-line (artificial intelligence) from Wikipedia
  18. ^ Fernand Gobet (2007). Chunk hierarchies and retrieval structures: Comments on Saariluoma and Laine. Scandinavian Journal of Psychology, 42. pdf
  19. ^ George Church, Yuan Gao, Sriram Kosuri (2012). Next-Generation Digital Information Storage in DNA. Science
  20. ^ Hybrid Memory Cube from Wikipedia
  21. ^ Intel Nehalem Core i3
  22. ^ 3D XPoint from Wikipedia

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