Static Random Access Memory (SRAM)

Definition - What does Static Random Access Memory (SRAM) mean?

Static Random Access Memory (Static RAM or SRAM) is a type of RAM that holds data in a static form, that is, as long as the memory has power. Unlike dynamic RAM, it does not need to be refreshed.

SRAM stores a bit of data on four transistors using two cross-coupled inverters. The two stable states characterize 0 and 1. During read and write operations another two access transistors are used to manage the availability to a memory cell. To store one memory bit it requires six metal-oxide-semiconductorfield-effect transistors (MOFSET). MOFSET is one of the two types of SRAM chips; the other is the bipolar junction transistor. The bipolar junction transistor is very fast but consumes a lot of energy. MOFSET is a popular SRAM type.

The term is prononuced "S-RAM", not "sram."

Techopedia explains Static Random Access Memory (SRAM)

There are two types of RAM: static random access memory (SRAM) and dynamic random access memory (DRAM). The main memory in a computer is dynamic RAM. All DRAM chips on Rambus in-line memory modules (RIMMs), single in-line memory module (SIMM’s) and dual in-line memory module (DIMMs) need to refresh every few milliseconds. (This is done by rewriting the data to the module.)

DRAM continuously refreshes 100+ times per second. Static random access memory (SRAM) is a lot faster and does not require refreshing like dynamic RAM.

While SRAM can operate at higher speeds than DRAM, it is more expensive to manufacture because of its complex internal structure, so most of the RAM on the motherboard is DRAM. As well, due to its condensed size it is not ideal for main memory. SRAM is best suited for secondary operations like the CPU’s fast cache memory and storing registers. SRAM is most often found in hard drives as disc cache. It is also found in compact discs (CD’s), printers, modem routers, digital versatile discs (DVD’s) and digital cameras.

SRAM’s access time is a lot faster than DRAM’s. SRAM is about 10 nanoseconds; DRAM’s access time is about 60 nanoseconds. Additionally, SRAM’s cycle time is a lot shorter than DRAM’s because it does not need to refresh. The cycle time of SRAM is shorter because it does not need to stop between accesses to refresh.

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