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Memory refresh is a process that
largely defines the characteristics of dynamic random access memory (DRAM),
which is the most used computer memory type. The process involves the periodic
reading of information from a certain section of the memory and the immediate
rewriting of the read information to the very same area without making any
changes. It is a background maintenance process that is necessary for operation of
DRAMs. When in operation, each of the memory cells needs to be refreshed
repeatedly. However, the maximum interval between two refreshes is defined by
the manufacturer of the memory and lies in the millisecond segment.
Techopedia Explains Memory Refresh
In a DRAM semiconductor chip, small
capacitors store each bit of data by the presence or absence of an electric
charge. Over the passage of time, these charges tend to leak away, which would mean
that loss of charge is equivalent to the loss of data. In order to counter
this, external circuitry is designed to read the data and then rewrite it
immediately, thereby restoring the charge on the capacitor to its normal level. Every
memory refresh cycle is also done as per a succeeding area of memory cells and
eventually refreshing every cell in a full cycle. The process happens
automatically in the background. Memory read and write operations are also not
available during the process of a refresh cycle, however, in modern memory
chips the time for overhead is so small that it usually does not noticibly slow down
memory operation.
