The Athlon 64 FX is the most powerful device in the AMD64 processor family - and its $1,000 per-unit cost also makes it the most expensive. In consideration of the price, customers get a slightly higher clock speed and the option to overclock the processor with the device's free multiplier selection capability. However, given the price, we only recommend investing in the device when maximum CPU power is required for very high-end - and almost always professional - computationally-intensive tasks.

AMD initially made only one FX model available. The Athlon 64 FX-51 (2.2 GHz) was the first version, but it was only available for Socket 940. Athlon 64 FX-53 (2.4 GHz) followed with the introduction of the Socket 939 platform, and it was replaced by the FX-55 (2.6 GHz). However, it was not phased out when the 2.8 GHz Athlon 64 FX-57 was released. According to AMD, demand existed for two different FX versions.

We assume that the FX-57 will still be around for some time following the introduction of the FX-60, since its clock speed makes it the fastest single-thread processor available from AMD. Also, some applications run marginally slower on dual-core processors compared to their single-core counterparts with the same clock speed (we found a 3.3% difference with WinRAR, for example). Yet this advantage will be short lived as more applications make use of thread-optimized multiple processing cores.

So why has AMD waited so long before launching a dual-core FX? AMD claims that the market was not ready, demonstrated by the lack of applications that could benefit from a second-processor core. However, AMD really believes that a dual-core FX premium processor should not be considerably slower than a single-core device, even in single-threaded environments. For AMD, it would be unacceptable for any dual-core device to run more slowly than a single-core CPU.

Athlon 64 FX Overview

Athlon 64 FX-60

The test motherboard recognized the FX-60 as a dual-core processor.

Any decent Socket 939 motherboard with an AGP or PCI Express chipset can host the Athlon 64 FX-60. It only has to be capable of supplying enough power to the processor. This can be checked by consulting either the motherboard manual (if it supports FX, it will technically support the FX-60) or by browsing the motherboard manufacturer's Website for an updated BIOS version, which almost all motherboard makers offer.

Nothing was changed inside the chip: There are two Athlon 64 cores on a single die, which is manufactured with AMD's 90 nm SOI process. SOI means silicon on insulator and refers to insulating layers that divide each of the structural layers in order to prevent leakage currents as much as possible. Leakage is responsible for high heat dissipation and thermal problems with Intel's 90 nm Pentium D and Pentium 4 processors.

Each core comes with its own 1 MB L2 cache. A crossbar switch allow for each core access to access the other core's L2 cache, while Intel's devices must utilize the Front Side Bus for every access.

AMD still offers the NX-bit (non-execute) feature, which helps to prevent buffer overflows within the main memory, AMD64 extensions and the energy-conserving Cool & Quiet capability. The latter, which requires BIOS support, allows the OS to ratchet down the clock speed to as low as 1 GHz to reduce power consumption and heat dissipation.

Windows XP logs recognizes two processing units with the Athlon 64 FX-60.