104 Watts: Is It a Lot or Not?

I haven’t yet met Athlon 64 processors with a thermal design power of above 89W, although the higher heat dissipation of the Athlon 64 FX-55 doesn’t shock me at all. It was a year ago that AMD warned mainboard manufacturers that support of a new thermal design power and higher CPU supply currents would be necessary for compatibility with future products of ratings 4000+ and higher and FX-55 and higher. Back then this warning was understood to concern future CPUs on 90nm cores.

The road map has been corrected, however, and the Athlon 64 4000+ with the Athlon 64 FX-55 come out on old 130nm cores and the former even fits into the older requirements to power consumption and heat dissipation. The latter, however, does not, and AMD applies new power specifications to it. Fortunately, these specs were formulated quite a long time ago, and all hardware manufacturers should have got ready to them. Let’s see if they really are and what problems an owner of an Athlon 64 FX-55 may expect to see due to the processor’s unusual thermal design power.

Mainboards first. AMD worded the new power and cooling requirements of upcoming Socket 939 processors about a year ago, long before the platform itself appeared, so the overwhelming majority of existing Socket 939 mainboards can work all right with the Athlon 64 FX-55. It means that the CPU power circuitry of such mainboards can output the necessary 80amp current. That said, there still can be some pitfalls. Particularly, the MOSFETs in the power circuitry may become too hot when you are using such a power-hungry processor. For example, the temperature of the MOSFETs on our ASUS A8V Deluxe mainboard was as high as 70-80°C during our tests of the Athlon 64 FX-55. This is certainly no good for them, and we’d recommend you to consider additional cooling of the CPU power circuit.

Second, the higher heat dissipation requires an appropriate CPU cooler, too. Many coolers for Socket 754/939/940 were developed when there was no info about the new TDP of Athlon 64 processors. It means you should pay attention to the cooler’s compatibility with the particular processor. For example, the Thermaltake Silent Boost K8 cooler we have been using long and successfully in our labs failed with the Athlon 64 FX-55 processor. With this cooler on, the Athlon 64 4000+ was 64°C hot, which is acceptable, while the temperature of the Athlon FX-55 under the same conditions was up to 83°C and that’s hardly a safe operational mode.