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.

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.

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.

But let's go back and take a closer look at the bandwidth of unbuffered dual-channel DDR memory in combination with an Athlon 64 processor. AMD claims a memory bandwidth of up to 6.4GBps which is very impressive, but does it hold true? Although we don't quote SisoftSandra scores any longer, due to it not being a benchmark as such, we still gave it a quick run to see how the numbers added up. AMD is not far off the mark with numbers higher than those of a Pentium 4 with the i875P chipset and PC4000 (500MHz) memory.

Comparing the old FX-53, which used buffered ECC memory, to the new Socket 939 model in PCMark 2004 the memory score was up almost 300 points. The result was not quite as high with the 3800+ but it still managed close to a 200 point improvement. This might not seem overly impressive, but compared to the single channel Socket 754 3400+ the PCMark 2004 memory score is up 1700 points for the 3800+ which is very significant.

We compared the 3800+ with the FX-53 in the graphs so you can see how they compare in terms of performance, and we now see little reason to go with the FX-53 as it doesn't seem to offer a significant boost in performance over the 3800+. This might, however, change with production motherboards and a faster graphics card, as the GeForce FX5900 XT card that is part of our standard test platform doesn't have enough grunt to really show off what these processors are capable of.

AMD claims that the FX-53 should offer in the region of 3-4 per cent performance advantage over the 3800+ in 3D games. But looking at the results from our 3D benchmarks this doesn't hold quite true, but as I said, this is partly down to our reference graphics card.

Neither chip comes cheap. The 939-pin FX-53 costs $799, the 3800+ $720, the 3700+ $710 and the 3500+ $500.

Overall the new Socket 939 platform is impressive and AMD's Athlon 64 platform is entering a new era, although many of the early Athlon 64 adopters might be disappointed at having to purchase a new motherboard and processor for their next upgrade. However, this is normal for life in the computer fast lane, constant change always leaves the early adopters having to pay the price. Hopefully AMD will stick with Socket 939 for some time now, as there is no logical reason to change it.

One final thing, for anyone thinking of getting one of the new processors, remember that later this year PCI Express will arrive for Socket 939, which means that if you want to be at the cutting edge, a motherboard and graphics cards upgrade is due in a couple of months. It might just be worth holding on a little bit longer and doing it all in one go. The only good news is that AMD is sticking with DDR400 memory for now, so there is no need to rush out and buy DDR2 modules for the new platform.

Verdict

AMD's new Socket-939 is what the Athlon 64 should have been from day one and will give Intel a real run for its money with excellent performance and hopefully a competitive price. AMD has yet again clawed back the performance crown from Intel, but for how long?

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