static RAM - technical definition

A fast memory technology that requires power to hold its content. Static RAM (SRAM, S-RAM) is used for high-speed registers, caches and relatively small memory banks such as a frame buffer on a display adapter. In contrast, the main memory in a computer is typically dynamic RAM (DRAM, D-RAM). Static RAM chips have access times in the 10 to 30-nanosecond range, while dynamic RAM is usually above 30 ns. Bipolar and ECL memories are under 10 ns.

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Static RAM is fast because the six-transistor configuration of its pretzel-like flip-flop circuits keeps current flowing in one direction or the other (0 or 1). The 0 or 1 state can be written and read instantly without waiting for a capacitor to fill up or drain; however, the six transistors take more space than dynamic RAM cells made of one transistor and one capacitor.