The phrase clock doubling implies a clock multiplier of two.
Examples of clock-doubled CPUs include:
- the Intel 80486DX2, which ran at 50 or 66 MHz on a 25 or 33 MHz bus
- the Weitek SPARC POWER µP, a clock-doubled 80 MHz version of the SPARC processor that one could drop into the otherwise 40 MHz SPARCStation 2
In both these cases the overall speed of the systems increased by about 75%.
By the late 1990s almost all high-performance processors (excluding typical embedded systems) run at higher speeds than their external buses, so the term "clock doubling" has lost much of its impact.
For CPU-bound applications, clock doubling will theoretically improve the overall performance of the machine substantially, provided the fetching of data from memory does not prove a bottleneck. In more modern processors where the multiplier greatly exceeds two, the bandwidth and latency of specific memory ICs (and/or the bus or memory controller) typically become a limiting factor.
Read more about this topic: CPU Multiplier
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