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Dual Graphics Platforms, Part II

How To Overclock The AMD Platform

Unlike Intel-based computers, an AMD system has no front side bus. Instead, HyperTransport is used to link the processor to the chipset. It has a system base clock of 200 MHz; a multiplier of 5 is applied in order to hit the 1,000 megatransfers per second for the HyperTransport protocol (which corresponds to 1,000 MHz here).

However, since the memory controller is part of the processor, there are fewer bandwidth requirements between the CPU and the chipset. A similar Intel Pentium 4 or Pentium D based system has to use the front side bus for every memory access, which adds latency to each operation. This all means that the resulting system or HyperTransport speed is far less important than one would believe with AMD based systems.

Despite this, a flexible overclocking range is still very important, in order to overclock either the CPU or the main memory, because the goal is to find the best performing combination of system speed, processor multiplier and memory clock speed. These tuning measures result in noticeable performance boosts.

Increasing The System Clock Speed

Every Athlon 64 motherboard other than the lowest cost models will offer you a BIOS option to alter the system clock speed. It defaults to 200 MHz with all Socket 939 processors, but clock speeds of almost 400 MHz can be reached today. However, this has more of an effect on other components than it has on performance, so be careful here.

Raising the system clock will automatically increase the HyperTransport speed as well, since as mentioned before, this is a multiple of the system clock speed. Look for an option called 'HTT Link' or similar. It should either be set to '1000 MHz' or to 5X, both of which mean that HyperTransport runs at five times the system clock speed. Possible options usually are 800 MHz (4x) and 600 MHz (3x). Whenever you overclock the system clock, make sure you reduce the HTT multiplier accordingly, because for the sake of system stability, you should not exceed the 1,000 MHz figure by much.