While Intel is very much the market leader, when it comes to discerning gamers, AMD’s Athlon FX-55 is the processor of choice. But with Intel’s 3.8GHz Pentium 4 670 snapping at its heels AMD has launched the Athlon 64 FX-57. This speed bump, from the 2.6GHz of the FX-55 to 2.8GHz, is a new megahertz high for AMD and has been done in order to keep Intel at bay so that it can still boast that it makes the fastest desktop processor.
Take a quick glance at the spec table and you’ll see that there have been some changes under the bonnet. The core of the FX-57 is the 90nm San Diego rather than the 130nm Clawhammer used for the FX-53 and FX-55, although you’ll also find some San Diego FX-55 processors on sale. San Diego is also used in the Athlon 64 3700+ and 4000+ models which have 1MB of L2 cache compared to the 512KB of the Venice core that is currently flavour of the month. Both Venice and San Diego use a silicon-on-insulator process and support the SSE3 instruction set. Intel has long led the way with SSE and while it seems to bring minimal benefit in the real world it can’t do AMD any harm to add this feature to its processors.
San Diego has an enhanced memory controller – it’s in the core with AMD processors, rather than in the chipset – so if you use four memory modules you should now find that they run at the correct speed. In the past some unfortunates have found that their PC3200 memory would mysteriously clock down to 333MHz if the controller got over-worked.
The main selling point of an FX processor is the unlocked clock multiplier, and if you delve into the tech specs a bit further you’ll see that this presumption that there will be overclocking has a significant impact on the power rating of the FX. The 3700+ and 4000+ San Diegos have an operating voltage of 1.5V and a TDP (Thermal Design Power) of 89 Watts so it doesn’t take much in the way of maths to see that the maximum current draw is 57.4 Amps, which is why AMD casually refers to the Athlon 64 as a 50 Amp part.
The FX-55 also runs on a 1.5V core voltage but the power rating is higher at 104 Watts, giving a current requirement of 69.3 Amps, and now we have the new San Diego FX-57 with a core voltage that has dropped to 1.4 Volts yet it has the same TDP of 104Watts as FX-55 which we calculate is a maximum current draw of 74 Amps although the official rating is 74.9 Amps. In conversation, AMD refers to FX-57 as an 80 Amp part, which is a huge amount of current for a motherboard to channel and the 104 Watts rating means that you need to use a beefy heatsink with the FX-57 with a heatpipe arrangement to get the heat away from the processor as fast as possible. A heatsink, indeed, just like the Thermaltake unit in the Press kit that AMD supplied for the FX57 review, with an Asus A8N nForce4 SLI motherboard and 1GB of Corsair CMX512 memory.