wait states : Computer Hardware Buyers’ Glossary

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©1997-2017 Roedy Green of Canadian Mind Products

wait states
Every year CPUs (Central Processing Units) get faster and faster, but RAM (Random Access Memory) lags well behind. The essential problem is RAM cannot keep up with the CPU (Central Processing Unit). So the CPU has to wait out a number of clock cycles for the RAM to produce the desired data. Depending on the relative speed of CPU and RAM, different numbers of wait state cycles are needed. Modern hardware configures this for you automatically. However, it is possible to override the settings in the BIOS (Basic Input Output System) and reduce the number of wait states. This makes the machine faster, but less reliable. This may be acceptable for a machine used only to play games.

CPUs try to get around these speed impedance mismatch by using layers of caches to avoid having to go to RAM for data. They also use lookahead to try to get fetch data from RAM long before it is needed. They also use dual cores, so that one CPU can continue operating while the other is waiting on RAM. They also use dual ported RAM so that two independent RAM fetches can go on simultaneously. I have this is my own machine. It is the main feature than speeds it up.

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