AMD Athlon 64 Socket 939

What the Athlon 64 should have been from day one?

Review It's finally here: the long-awaited Socket 939 Athlon 64 platform. But what does it bring with it and does it live up to the hype? So far there has been much speculation about the support of unbuffered dual-channel memory, which should boost the performance of the Athlon 64 close to the level of the high-end FX range of processors and possibly beyond, writes Lars-Goran Nilsson.

Socket 939 is the new consumer-level socket for all future Athlon 64 processors, although so far AMD has not officially declared what will happen to Socket 754. Rumour has it that this will become the new budget platform. Apart from unbuffered dual-channel memory support there are very few changes, but those with earlier Athlon 64 processors will notice that the cache has been cut in half. You only get 512KB, compared to the 1MB seen on the 3200+ and 3400+. This shift will happen all across the board and only the FX parts will now ship with 1MB of cache.

AMD Socket 939

The HyperTransport bus has also been given a boost, up from 1.6GHz to 2GHz, which should have an impact on performance for on-board Gigabit Ethernet and other high bandwidth sub-systems. This is, however, chipset dependant. Fortunately, the MSI 6702E motherboard we used to test the processors is based on the VIA K8T800Pro chipset, which supports the faster HyperTransport bus.

AMD supplied an FX-53 and a 3800+ to have a look at, so this article will give you a good idea of how the different processors will perform under similar circumstances. Both processors are clocked at 2.4GHz, which is 50MHz slower than the 3700+ Socket 754 part. This might seem strange, but AMD's reasoning is that the extra memory bandwidth and the faster HyperTransport bus should more than make up for the slightly lower CPU frequency.

AMD Socket 939 Athlon 64 processors

Other improvements will follow later this year, such as PCI Express support, but since this is limited to chipset support and no announcements have been made so far from any of the chipset vendors when such a product will be finalised. There is, of course, still support for AMD's PowerNow... er... Cool'n'Quiet technology that allows the processor to slow down if it is not fully utilised and thus produce less heat which in requires less active (slower and quieter) fans.

AMD also claims that a new feature will be available when Microsoft releases Service Pack 2 for Windows XP, which is what AMD calls Enhanced Virus Protection or EVP. This will work with any Athlon 64 processor and is not limited to the new Socket 939 models. EVP sets a part of the system memory aside as "data only" memory. This prevents any code resident in those memory areas from being executed as it can only be read or written to. This means that memory overflow viruses will not affect a system with EVP enabled.

How well this will work in practice and how many such viruses there are out there is something we will see when Service Pack 2 arrives later this year. It is a good initiative by AMD - Transmeta, too, which will add the feature to its Efficeon processors - but most viruses are far more complex these days. That said, anything that helps protect your PC is a good thing.

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