dynamic RAM

dynamic RAM

The most common type of computer memory. Dynamic RAM (DRAM, D-RAM) chips are very dense because they use only one transistor and one storage capacitor for each bit. Unlike non-volatile firmware chips (ROM, EEPROM, flash, etc.), both major types of RAM, dynamic RAM and static RAM, lose their content when the power is turned off.

Capacitors were used in the 1960s for computer memory, but dynamic RAM was patented by IBM in 1968. The first commercial chips came from Intel and Mostek in the early 1970s.

Dynamic RAM Is a Total Loser
The capacitors in a dynamic RAM chip are electrical storage tanks that do a poor job of holding a charge. They constantly leak, and the chip would lose its content even when the power is on if it were not for the refresh circuitry that continuously re-energizes the capacitors approximately 15 times per second. However, even with the refresh circuitry, dynamic RAM cells take up significantly less space than static RAM cells. Contrast with static RAM. See memory types.

A Dynamic RAM Cell

DRAM cells are very simple. The combination of voltage on the row and column lines charges a capacitor. The only problem is that the capacitors keep losing their charges, and the bits must be read and re-written hundreds of times per second.

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dynamic RAM - dynamic random-access memory