Clock doubling
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Clock doubling is a technique used to improve the performance of computers by doubling the speed of the CPU compared to the bus. For instance, if the computer's main clock runs at 100MHz, a clock-doubled CPU would run, internally, at 200MHz. This is a simple way to improve the performance of the CPU without having to improve the rest of the components in the system at the same time.
In theory for "compute intensive" applications where the memory performance is not important this technique will improve the performance of the machine by up to 100%, but generally the gains are smaller and the processor is starved for data.
- cleanup below
The most famous example of a clock-doubled CPU is the Intel 80486DX2, which ran at 50MHz on a 25MHz bus. Another example was the Weitek SPARC POWER µP, a clock-doubled 40MHz version of the SPARC processor that could be dropped into the otherwise 20MHz SPARCStation 2. In both cases the overall
Today almost all processors run at a different speed than the underlying bus, but the terminology is no longer used.