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Memory refresh is a charging cycle that a computer's random access memory (RAM) goes through on a periodic basis. When the computer reads data, the information is stored as a 1 or 0, on or off, respectively. To ensure the 1 sections do not lose their energy and that the information does not disappear from the RAM, that section of the memory is recharged. If the memory refresh cycle did not occur, then any information read by the computer would disappear in a few milliseconds. While all types of RAM go through a refresh cycle, dynamic random access memory (DRAM) does it most often because it has a capacitor unit for each piece of data.
When a computer opens an application and goes through any data or does anything, it reads the information in binary. Binary is a computer language consisting of 1's and 0's, with 1 meaning on and 0 meaning off. When there is a 0, that part of the information does not need any electrical charge because it is off; if there is a 1, then an electrical charge is needed to turn the memory on. With an electrical charge, the memory is able to display any information requested by the user.
The charge is only temporary. Without memory refresh, the charge would disappear, turning all the sections on the RAM to 0, and no information could be displayed or stored for long. It only takes a few milliseconds for the charge to completely disappear.
To fix this problem, either a memory controller unit or the central processing unit (CPU), depending on the model, visits the RAM. Any section marked as a 1 receives an electrical charge to ensure the section does not power down. This process goes on automatically, without user instruction, and occurs thousands of times in a single second. By doing a memory refresh, the computer can hold any information; with high amounts of refreshing, however, this also drains a considerable amount of power and slows down the computer.
All versions of RAM go through a memory refresh, but the one version of RAM that has it the most is DRAM. The main difference between DRAM and other RAM units is it is constructed to hold each section of data in a separate capacitor unit. This makes the information easier to store, but also makes it more volatile if the memory refresh cycle does not recharge the DRAM stick.