Trying to figure out whether to go for an AMD CPU or an Intel one isn't as simple as comparing the speeds and feeds. Both platforms need to be taken into consideration so that you can compare the costs effectively and make sure you buy the right components to fit your budget. AMD claims to have a winner in this respect, as its new AMD Phenom II X4 CPUs are based on the same socket design as the previous Phenom and won't require a completely new motherboard and memory in order to function properly.

That's good news for owners of AMD-based PCs — specifically ones that use the AM2 CPU socket design — but even users who are contemplating building a new PC should take a look at what the Phenom II X4 offers, because it is AMD's best CPU to date.

The Phenom II X4 940 Black Edition CPU is currently AMD's cream of the crop for desktop users and can be purchased for $500-$550 (based on a quick search using Statice.com.au). Make no mistake, though, it's not designed to compete against Intel's Core i7 chips, but instead against the Core 2 Quad range.

The Phenom II X4 940 is a quad-core, 64-bit CPU with a clock speed of 3GHz and three levels of cache; there are small amounts of level 1 (128KB) and level 2 (512KB) cache for each individual core, as well as a shared 6MB level 3 cache for all cores to use. AMD retains an integrated memory controller, which supports DDR2 memory up to 1066MHz.

The chip has been built using AMD's 45 nanometre manufacturing technology, which means it has smaller transistors than the previous Phenom CPUs and can run faster and cooler while consuming less power. The Phenom X4 9950 had a power rating of 140W and was formerly AMD's fastest CPU, while the Phenom II X4 940 has a power rating of 125W. This is only five Watts less than Intel's speed-comparable Core 2 Extreme QX9650, which is rated at 130W (but doesn't have an integrated memory controller).

We tested the 940 on a 32-bit Wndows Vista platform running an MSI 790GX–based motherboard, 2GB of Kingston DDR2 1066MHz RAM, on-board ATI graphics and an 80GB solid-state drive from Intel. The system consumed 152W of electricity when all four of its cores were under a full load, which is a decent result for a powerful system. And it is powerful: in WorldBench 6 it recorded a score of 122, which makes the fastest AMD CPU we've seen by far and also puts in good company with Intel's Core 2 Extreme QX9650, which is a ludicrously more expensive beast that averages around 130 in WorldBench 6.

In our Blender 3D rendering test the Phenom II X4 940 recorded a time of 36sec, which is good; it means, of course, that a system based on this CPU will do very well when encoding videos and music, as well as decoding high-definition video streams. In fact, if you opt for this CPU, motherboard and RAM configuration, you'll be able to build yourself a punchy workstation or media centre PC for less than $1000 (using a conventional hard drive).

Compared to the previous generation of Phenom CPUs, the Phenom II CPUs have a larger level 3 cache as well as faster frequencies. The 940 runs at 3GHz, but AMD is confident that it can be overclocked significantly while using an air-based cooler. During our tests using the standard AMD cooler the 940 did indeed run without problems at 3.4GHz, but it was unstable at 3.5GHz. The gain in performance in Blender 3D was 6sec, which is nothing to scoff at, so with a little fine-tuning more performance can be obtained from this CPU. We manipulated the clock speed through the BIOS, but AMD also has an Overdrive utility that lets you bump up the speed of your system directly through Windows. You won't see significant gains by using this utility — Blender 3D only gained one second when we ran Overdrive in "high performance" mode.

Anyone who owns an AM2-based motherboard should be able to plug in the AMD Phenom II X4 940 but there are no guarantees, and you should check your motherboard vendor's site to make sure it will be supported — in some cases a BIOS update might be needed. However, if the Phenom II is used in a motherboard with an AM2 CPU socket it will not run optimally. Its full-duplex HyperTransport link will only run at 2GHz rather than 3.6GHz if run on a motherboard with an AM2+ socket. This release from AMD is a return to form for the company that once had Intel on its knees. The Phenom II 940 puts up respectable numbers against a Core 2 quad-core CPU, and it's much better value. We think it's worth considering the Phenom II if you're in the process of configuring a new quad-core machine for home or workplace use, or even for a media centre PC. Our configuration with integrated graphics worked a treat.