- Memory refresh
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Memory refresh is the process of periodically reading information from an area of computer memory, and immediately rewriting the read information to the same area with no modifications. Each memory refresh cycle refreshes a succeeding area of memory. Memory refresh is most often associated with modern dynamic random access memory. Due to the problem of fading of charge in DRAM information stored in capacitors become 1's to 0's.To prevent this from happening,design engineers adds an extra circuitry to recharge cells periodically. This process is refresh. If a cell is less than half recharged,it is determined to be zero,and cell is not recharged.
However, several early computer memory technologies also required periodical processes similar in purpose. These technologies include delay line memory and Williams tube.
Compare with magnetic core memory where each memory cell needs to be refreshed after being read, but periodical refreshes are not necessary. Also, see static random access memory which is used in similar applications as dynamic random access memory, but does not require refreshing (hence labelled static as opposed to dynamic).
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