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Old 31st March, 2004, 04:29 PM
Aedan Aedan is offline
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Join Date: September 2001
Location: Europe
Posts: 13,075

The GPU and other components are driven from clock signals derived from a crystal. As the fundimental frequency of this crystal is too low, it is multiplied upwards by a PLL. As the PLL can be programmed to provide a particular frequency, all the software tools do is change the multiplication used by the PLL.
Hence, to overclock a GPU or memory, you just have to reprogram the PLL's internals.

Now to the other part of the problem! It's not the moving of the electrons - they'll move when you apply a potential difference across them. The problem is making out the difference between a 1 and a 0 when the data gets to the end of a transmission line. Increasing the voltage to the I/O buffers helps to increase the difference between a 0 and a 1, and hence increases the noise margin.

Heat causes a problem too, as the hotter a component gets, the larger the thermal noise that is generated. Once this noise gets to the point it could be misintepreted as a 0 or as a 1, then the game is over. This happens easily, as at RF frequencies, the I/O buffers will be seeing a bunch of cascading edges, rather than discrete voltage levels.

Once you look into high speed logic design, you begin to realise that it's amazing anything works at all!
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