AMD has had a busy few weeks announcing and releasing a whole raft of dual-core processors. The first wave of products came on the 21st of April when it released three dual-core Opterons in the 8xx series, which are for 1-8 way servers.

AMD has continued to use its existing Opteron model code system so the new processors are called 865 (1.8GHz), 870 (2GHz) and 875 (2.2GHz) with official prices (per CPU, in trays of 1,000 units) of $1,514 (865) and $2,149 (870), while the 875 costs $2,649.

At the same time that it launched the 865, 870 and 875, AMD also announced the 2-way Opterons which will go on sale in May. The 265 ($851), 270 ($1,051) and 275 ($1,299) are much more reasonably priced than the dual-core 8xx models but that is exactly the reason why AMD has launched these new dual-core processors from the top down, instead of using Intel's approach of launching the dual-core Pentium Extreme Edition for the desktop PC market.

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If you have a four-way server that is running a full complement of Opterons then up to now the only way to add more processing power is a fairly serious upgrade of the server chassis and motherboard to make it eight-way. The dual-core Opteron brings a new set of options for IT managers as they can now replace the four Opterons in a server with four dual-core processors and bingo, they have eight physical processors on the same four sockets, while an eight-way can effectively become a 16-CPU server.

This isn't Hyper Threading or virtualisation, but instead we're talking about two physical processor cores that are joined by what AMD calls a crossbar. Each Opteron core has its own L2 cache and as each core has its own memory controller the processors are able to deal with data far faster than the Intel Pentium D and Pentium Extreme Edition, which have to communicate through the Northbridge of the chipset to access the system memory.

The key point of the dual-core Opterons is that they use the same Socket 940 form as the regular Opteron and they work with the same chipsets as Opteron, so all you need is a BIOS update to allow you to upgrade your server to dual-core. Although the processors are relatively expensive, the fact that you can retain all of your hardware with no need to reinstall any software means that the total cost of the upgrade is actually low.

Well that's all fine and dandy but you probably don't run Opterons in your home PC, and if you do it's likely to be from the 1xx single processor family. AMD hasn't announced its intentions with regard to this type of Opteron but we believe that it will go dual-core and will also move from Socket 940 to Socket 939, so it will effectively be an Athlon 64 which supports ECC memory. Remember, the memory controller is part of the processor.

AMD has also announced Athlon 64 X2, which is the dual-core version of Athlon 64 that is due for release some time in June. AMD has elected to use a model code system that continues from the current Athlon 64 4000+ which has a clock speed of 2.4GHz and 1MB of L2 cache.

With Athlon 64 X2 AMD has completed the move from a 130nm (0.13-micron) fabrication process to 90nm SOI (Silicon On Insulator), in part because it had to make the cores smaller to fit two of them on to a single processor socket successfully. Although the second core raises the transistor count to 233.2 million, thanks to the 90nm fabrication process the die size is only a few square millimetres larger than 130nm SOI Athlon 64 that you can currently buy.

AMD has also enhanced the memory controller so it works with a greater range of memory, as well as adding most of the SSE3 instruction set. Athlon 64 X2 will be released in four models, running at either 2.2GHz or 2.4GHz, with either 512KB or 1MB of L2 cache on each core.

The X2 4200+ runs at 2.2GHz with 512KB of L2 cache on each core, the 4400+ is 2.2GHz and 1MB, the 4600+ jumps to 2.4GHz with 512KB cache and the 4800+ has the full monty at 2.4GHz with 1MB of L2 cache on each core. Official AMD pricing, which is per CPU, in US dollars and for a tray of 1,000 processors, is $537 (4200+), $581 (4400+), $803 (4600+) and $1,001 (4800+), so you can probably expect to pay £700 for the Athlon 64 X2 4800+ at UK retail prices.

The Athlon 64 X2 is pin compatible with the current Athlon 64 so you can upgrade after a BIOS flash, with one proviso. X2 has a maximum requirement of 80A which shouldn't cause too many problems for a decent motherboard, however some cheaper models are built to supply a maximum of 60A so they won't allow a shift to dual-core.

That leaves the big question, what benefit does dual-core offer that a single core can't match?

There's no doubt that the two physical cores allow Windows or Linux to split the workload, so where an application such as anti-virus software or graphics rendering currently takes all of the available processor power, with dual-core you'll find that one core remains available for other tasks, which means that your PC doesn't freeze solid because it's busy.

The other benefit is performance, although this is a bit of a mixed bag. If you're running a single threaded application, such as Doom 3, then what you want is clock speed and memory bandwidth. The Athlon 64 FX-55 is the fastest processor that you can buy for gaming, and that's all there is to it.

If your workload is more varied then you can expect to see X2 perform much as the model number suggests, despite its slightly lower clock speed, but if you run multi-threaded applications then dual-core has a serious advantage. We ran graphics rendering tests under both 32-bit and 64-bit Windows, as well as the Sysmark 2004 test suite in 32-bit Windows XP and the new Opteron and Athlon 64 X2 were absolutely mind-blowing.

We were already impressed, but the icing on the cake was the way that Athlon 64 X2 4800+ was able to run our benchmarks with an operating temperature of less than 40 degrees Celsius.

From the first, AMD designed the Opteron and Athlon 64 with multi-core scaling in mind and it has paid off magnificently. We are deeply impressed by the way that these new processors operate so efficiently on relatively little power and as a result they throw out very little heat. This is in marked contrast to Intel's dual-core Pentium 4, and we reckon that the Athlon 64 X2 4800+ is the best desktop processor that we have ever used.