AMD Athlon 64 FX-55 & Athlon 64 4000+

Processor Details & Overclocking

We tested the Athlon 64 FX-55 and the Athlon 64 4000+ with an assortment of high-end supporting parts, including 1GB of low-latency Corsair PC3200 RAM (2-2-2-5), an NVIDIA GeForce 6800 GT, and a motherboard powered by NVIDIA's nForce 3 Ultra chipset, the MSI K8N Neo2 Platinum.  Regular readers may remember the MSI K8N Neo2 Platinum from a recent Socket 939 motherboard round-up posted here on HotHardware, where we gave the board our Editor's Choice award...

The Athlon 64 FX-55 & 4000+: Up Close & Personal
AMD's Latest Power Plants



Before installing the processors into our test bed, we snapped a few pictures to give you a closer look.  The Athon 64 FX-55 and 4000+ obviously look very similar except for the markings etched into their respective heat spreaders. They both have green organic packaging and, obviously, both have the same 939-pin configuration. From a physical standpoint, not much has changed since we initially took a look at the first Socket 939 Athlons 64s back in June.

However, the cooler that will be packaged with AMD's PIB (Processor In a Box) products has been updated.  The new model has a copper base with liquid-filled heat pipes that lead from the base to the thin aluminum fins. We found this cooler to be relatively quiet, and it worked quite well.  If our MSI motherboard was reporting temperatures properly, neither the Athlon 64 FX-55 nor the Athlon 64 4000+ ever broke the 50 degree Celsius mark, and they idled at just barely over 40 degrees C.

Overclocking The AMD Athlon 64 FX-55 & 4000+
Default & Overclocked Speeds & Temps

AMD Athlon 64 4000+
(12 x 200MHz = 2400MHz)

AMD Athlon 64 FX-55
(13 x 200MHz = 2600MHz)

Before we began benchmarking these new processors, we fired up CPU-Z and SiSoft SANDRA to see if there was anything interesting to report.  Other than the Athlon 64 FX-55's and Athlon 64 4000+'s clock speed, nothing much has changed since we last looked at the Socket 940 Athlon 64 FX-53 back in March.  As you can see, both of these processors are built using AMD's 0.13-micron manufacturing process and are similarly clocked at 2.6GHz (13 x 200MHz) and 2.4GHz (12 x 200MHz) by default.

AMD Athlon 64 4000+
Overclocked - 2.69GHz

AMD Athlon 64 FX-55
Overclocked - 2.82GHz

We also spent some time trying to overclock the new Athlon 64 FX-55 and 4000+ and had some very interesting results.  To overclock these processors, we used the stock AMD copper / aluminum heatsink and fan combo pictured above in an open air environment.  With more exotic cooling, our overclocking results would likely have been different.  Keep that in mind, as your mileage may vary. 

We bumped the CPU voltage up by 3.3% and the memory voltage to 2.85v and gave all of the other peripherals a .1v bump, as well.  Then we lowered the speed of the HT link and raised the processor's bus speed until the test system was no longer stable.  In the case of the FX-55, because the CPU is unlocked, we raised the multiplier first before cranking up the bus speed.  Lower multipliers are available on all "Cool'N'Quiet"-enabled Athlons, such as the 4000+, but because we were trying to find each processor's top speed and not the motherboard's, we used the highest multipliers possible.

Ultimately, we were able to take the new FX-55 up to an impressive 2.82GHz, a 220MHz (8.4%) increase. It seems the strained silicon-on-insulator technology used on the FX-55 has given AMD a bit more headroom to play with in regard to clock speed.  The Athlon 64 4000+ was also fairly cooperative. We were able to raise the 4000+'s clock speed to 2.69GHz, a 290MHz (12.1%) increase.

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