PC mechanic

Static RAM (SRAM). This RAM will maintain it’s data as long as power is provided to the memory chips. It does not need to be re-written periodically. In fact, the only time the data on the memory is refreshed or changed is when an actual write command is executed. SRAM is very fast, but is much more expensive than DRAM. SRAM is often used as cache memory due to its speed.
There are a few types of SRAM:
Async SRAM. An older type of SRAM used in many PC’s for L2 cache. It is asynchronous, meaning that it works independently of the system clock. This means that the CPU found itself waiting for info from the L2 cache.
Sync SRAM. This type of SRAM is synchronous, meaning it is synchronized with the system clock. While this speeds it up, it makes it rather expensive at the same time.
Pipeline Burst SRAM. Commonly used. SRAM requests are pipelined, meaning larger packets of data re sent to the memory at once, and acted on very quickly. This breed of SRAM can operate at bus speeds higher than 66MHz, so is often used.

This site has more info on ROM, RAM and DRAM.
from PC mechanic.

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