Tech moves fast! Stay ahead of the curve with Techopedia!
Join nearly 200,000 subscribers who receive actionable tech insights from Techopedia.
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.
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.