X-bit labs

AMD Raises the Bar: AMD Athlon 64 FX-55 and AMD Athlon 64 4000+ CPUs Review (page 5)

Category: CPU

by Ilya Gavrichenkov

[ 10/18/2004 | 09:00 PM ]

That’s why AMD sent us a more advanced cooler on heat pipes (made by AVC), specially for testing the Athlon 64 FX-55:

The use of the Athlon 64 FX-55 has also implications concerning the power-supply unit, especially if you’re planning to overclock this processor. You can get an estimate of the required wattage, basing on the averaged data from the following table:

Thus, a simple computer system with an Athlon 64 FX-55 processor, a powerful graphics card, a single hard disk drive and one optical drive will require a 350W PSU at the very least. And this PSU must provide a current of at least 18amp on the +12v power rail.

Then, you must keep in mind the fact that the power consumed by the processor grows dramatically at overclocking. It is described by a simple formula:

Power=a*c*F*V²,

where a is a coefficient that is proportional to the average CPU load, c is a coefficient that depends on the CPU architecture, F is the frequency, and V is the processor core voltage. So, while the Athlon 64 FX-55 clocked at its regular 2.6GHz frequency and with the normal 1.5v voltage consumes up to 104W under the maximum load, it will consume up to 140W if you overclock it to 2.8GHz and increase its voltage to 1.65v. The overclocked system with an Athlon 64 FX-55 must use a high-quality 400W PSU at least in this case.

Well, this guarantees nothing, too. It’s always better to have a margin of safety for the PSU. I ground this recommendation on my own experience, by the way, as our 400W Zalman ZM400B-APS PSU, which has been working in our testbed for about a year, successfully handling the Prescott and the Pentium 4 Extreme Edition, crashed during our tests. It crashed during our overclocking tests, to be exact, so this confirms the formula above and its consequences.

Summarizing this section of the review, I want to say that Socket 939 processors with the new TDP (right now there’s only one such processor – the Athlon 64 FX-55) pose strict requirements to the hardware parts you use in your computer system.