Choosing an AMD processor can be very confusing, with varying cores, pin counts and strange PR ratings. With the advent of the new Sempron processor, we felt it would be a good idea to take a look at this subject with a focus on their new budget option.

Athlon 64's are available across three different platforms. Socket 754 is for the Athlon 64 and Sempron. Socket 940 is for Opteron and Athlon FX (recommended for those who have more money than sense). Socket 939 supports both Athlon 64 and FX chips.

Without a doubt, Socket 939 offers the best future protection being compatible with the latest Athlon 64 and FX chips. We also see support for dual channel memory, something Socket 754 doesn't support. Unfortunately, availability is currently quite poor - both of the boards and of the chips. Socket 940 is pretty much a dead platform as far as the consumer is conerned. The future of socket 754 s questionable, but at the moment it is certainly the best value for money and by far the most available.

With the VIA K8T800 Pro and nVidia 250GB chipsets out and about, overclocking is finally a reality with the Athlon 64, thanks to functioning AGP and PCI locks. Implementation of this has been difficult though, so not all boards support this. It may be worth reading our Athlon 64 motherboard round up here to aid your decision. Chipsets used for Socket 939 motherboards are pin compatible with Socket 754, so when PCI Express support arrives, it is quite plausible that Socket 754 may also see the same upgrade. With the memory controller integrated onto the processor, one thing we won't be seeing is DDR2 support.

Which CPU?

On Socket 754, the biggest difference between chips is that of Level 2 cache. This can be quite confusing, especially when hidden behind the cloud of their often misleading rating system. The first chips produced where based on the "Clawhammer" core and came with 1024K of Level 2 cache. With the introduction of the "Newcastle" core, they decided to reduce the amount of cache to 512K, while boosting the respective clock speeds by 200MHz as compensation. For example, a 3200+ Clawhammer clocks in at 2000MHz with 1024K of cache, while a 3200+ Newcastle core clocks in at 2200MHz with 512K of cache. To confuse matters even more, there are even some 512K Clawhammer chips where half the cache is disabled.

By reducing the amount of Level 2 cache on die, yields are increased, less heat is produced and higher clock speeds can be achieved. This generally means cheaper prices, excellent availability, less heat and good overclocking potential. When creating a die with 512K of cache, there is a high chance there will be some chips where the cache isn't quite up to standard. AMD can then disable the bad half of the cache rebadge it as Sempron.

The AMD Sempron is initially being introduced on the Socket 754 platform at a speed of 3100+. It is also being introduced on the Socket A platform, but this is based on a Thoroughbred core. The Sempron is designed with the same principles in mind as the Duron - a high value, budget microprocessor. The chip is a crippled Newcastle core, with only 256K cache and no 64-Bit support. The 3100+ runs at the speed of 1.8GHz on a 200MHz FSB. In comparison to other Athlon 64's, this rating is rather ambitious, but in fact the rating is supposed to be relative to an Intel Celeron.

The AMD Sempron looks physically identical to the Athlon 64

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