AMD this week launched its AM2 CPU socket, bringing support for fast DDR2 memory to the company's desktop processors. As expected, PC Advisor's sister title PC World's tests showed negligible performance gains from the socket, but the change positions AMD for more notable performance gains with future products.

Socket AM2 is a 940-pin technology that replaces the company's Socket 939 on motherboards, and it works only with AMD processors that support DDR2 memory instead of DDR. The new socket includes a four-bolt tray to offer a more stable platform for the processor heatsink.

In addition to the immediate availability of same-priced AM2 versions of most of its existing 939-based Sempron, Athlon 64 and Athlon 64 X2 processors, AMD announced the launch of two AM2-only processors. The company's new top-of-the line 2.8GHz Athlon 64 FX-62 will sell for about $1,031 (£555) and supports up to 800MHz DDR2; the new 2.6GHz Athlon 64 X2 5000+ will sell for about $696 (£375) and it and all the new AM2 X2 chips support up to 667MHz DDR2.

In addition, the company is now offering lower-watt versions of its X2 processors for use with Socket AM2 motherboards. The new energy-efficient models drop the maximum power specification from 110W to 85W. Each reduced-power X2 chip carries a small price premium over the standard X2 version.

AMD says it expects motherboards that support the new AM2 standard to begin shipping immediately from a wide range of vendors, including Abit, Asus, Biostar, ECS, EPox, Gigabyte, Leadtek, MSI and Shuttle.

The PC World Test Center ran a series of benchmarks to test the impact of AM2 on overall system performance, and to compare the previous high-end chip (the FX-60) to the new top dog (the FX-62).

Because Socket AM2 and Socket 939 aren't compatible technologies, we had to use two different motherboards. However, both of our test boards came from Asus, and both use versions of nVidia's nForce chip set. The rest of the system consisted of 2GB of RAM from Crucial (DDR2-667 for AM2 and DDR-400 for 939), two SATA hard drives in a RAID 0 array, an nVidia GeForce 7800GT-based graphics card and a 500-watt power supply.

To test the AM2 technology we dropped the clock speed of the new FX-62 to 2.6-GHz to match our FX-60 system. The result: an excellent WorldBench processing speed score of 133.

While the final scores matched, some notable scoring variations appeared in the applications that make up WorldBench. For example, in the ACDSee PowerPack test, the AM2 system finished in 420 seconds, while the 939-system took 431 seconds. And in our Microsoft Office 2002 test, the AM2 system finished in 502 seconds, versus 526 for the 939 system.

The tables turned in our two Mozilla-based tests, however. In our standard Mozilla test, the 939 system completed the task in 292 seconds versus 320 for the AM2 system. And in the Mozilla and Windows Media Encoder test, the AM2 system took 373 seconds to finish, while the 939-system completed the test in 358 seconds.

These differences, however, probably wouldn't be noticeable during regular usage. And in the vast majority of the other tests, the two systems posted results that were within seconds of each other.

When we ran the new FX-62 chip at its native 2.8GHz speed, we did see the expected performance boost. It notched an impressive WorldBench score of 137. That's not the fastest desktop we've tested (Xi Computer's MTower 64 AGL-SLI desktop with its dual 10,000-rpm hard drives continues to claim that crown with an impressive 147), but it's within striking range.

AMD has been actively working to lower people's performance expectations surrounding AM2, and it's clear why. The new technology really isn't about achieving better performance from existing parts - it's about moving the company's desktop processors to a unified socket that supports the now-industry-standard DDR2.

Bottom line, the new AM2 motherboards and processors shouldn't carry a premium over today's 939 versions. So if you're building or buying an AMD-based desktop, you should be sure to get a rig with the new technology.

There's certainly a growing perception that Intel has AMD's high-flying Athlon processors in its sights with the upcoming Core 2 Duo processor. Formerly coded-named Conroe, the new chip features a speedy new architecture and is due out in the second half of the year.

Preliminary public tests of Conroe showed sizeable performance gains over Intel's existing desktop processors, which have long trailed AMD's top chips in performance. If AMD hopes to keep hold of its performance crown, the company will need to add something besides AM2 to the mix.