Verdict: You'd have to be stark raving mad to buy any of these processors.

The Athlon 64 FX 7-series (also known in some circles as the Quad FX platform) arrived too late for last year's CPU Labs megatest. It represented AMD's desperate attempt to produce something that could compete with the Core 2 Quad and Core 2 Extreme that Intel had just launched.

Why would we describe the company's effort as desperate? Mainly because AMD couldn't make a quad-core CPU (in fact, it's only just started, more than a year after Intel), so its only answer was to put two dual-core CPUs on one motherboard. The end result was the FX 7-series, which was nothing more than a pair of tweaked Opteron 2200-series CPUs that could use standard rather than registered DDR2.

Despite using the same Socket F packaging as the Opteron 2200-series, the FX 7-series needed a new core logic chipset, nForce 680a, for which only one motherboard - the Asus L1N64-SLI WS - was ever made. The L1N64-SLI WS is fitted with four DIMM sockets (two per CPU) and four high-speed PCI-E slots if, for some bizarre reason, you wanted to run two graphics cards in SLI, and then another two graphics cards powering extra monitors.

AMD only ever launched three different FX-7-series CPUs, the FX-70, FX-72 and FX-74. All have two cores, each with its own separate 1MB of Level 2 cache, support 64-bit instructions, SSE3, Enhanced Virus Protection and Cool n Quiet. The FX-70 is clocked at 2.6GHz, the FX-72 at 2.8GHz and the FX-74 at 3GHz. At the time of launch, AMD made a big song and dance about how it would launch quad-core FX 7-series CPUs that you could simply drop into the L1N64-SLI WS within a few months. This clearly didn't happen, but AMD has told us that quad-core Phenom FX processors that can be used in the L1N64-SLI WS will be launched next year.

As the FX7-series is AMD's first attempt to make a quad-core platform for enthusiasts, we were keen to see how well the CPUs cope with modern applications and games. However, the two FX-70 CPUs were disappointingly slow, achieving an overall score of 842 in our Media Benchmarks. The FX-72 and FX-74 fared little better, notching up scores of 912 and 954 respectively. Our two test games appeared to like the four cores that a pair of FX 7-series CPUs provides, but none of the models could keep up with the latest Intel CPUs.

However, worse was yet to come. During testing, the L1N64-SLI WS became so hot that we could barely touch it - despite it having three crossflow fans mounted on the VRM heatsinks. This is due to the fact that the Quad FX platform is incredibly energy-inefficient. At full load, the pair of FX-74s drew a ludicrous 493W from the mains, exactly double that of a system fitted with a faster-performing quad-core Xeon X3210. The FX-72 and FX-70 proved to be barely any more energy-efficient than the FX-72, guzzling an astonishing 479W and 460W respectively. As if that wasn't bad enough, the FX-70 system drew more power than a dual-processor Xeon X5482 system with eight cores each running at 3.2GHz; as you'd expect, the Xeon X5482s destroy the FX-70s when it comes to performance.

However, the FX-7-series isn't only poor compared with Intel CPUs, but it's also poor compared with other AMD CPUs - the FX-74 system drew 130W more than an identically clocked Opteron 2222 system.

If you were unfortunate or foolish enough to build an FX 7-series system, you'll probably already be feeling the pinch as you try not to look at your electricity meter while awaiting the completion of tasks. For anybody else, we'd advise steering well clear of the FX 7-series of clunky, slow, electricity-guzzling, hot-running CPUs.

If that still isn't sufficiently direct, and you're still tempted by this curiosity, then it's worth pointing out that a single Xeon X3210 isn't only faster than a pair of FX-74s in most applications, but also almost a quarter of the price (£137.13 as opposed to £514.66). The Xeon X3210 is also more energy-efficient (246W compared with 493W) and doesn't require a silly overheating proprietary motherboard.

• Media PC components - 22nd August 2008
• PSUs - 14th July 2008
• Multi-GPU graphics - 20th June 2008
• CPU water cooling - 17th June 2008
• Hard disks - 20th March 2008
• Audio hardware - 29th February 2008
• Graphics cards - 24th January 2008

• Samsung SATA SSD 32GB - Hard disks / storage
• Spore - Games
• Zalman VF1000-LED - Other cooling hardware
• Arctic Cooling Accelero S1 Rev 2 - Other cooling hardware
• Antec Mini P180 - Cases
• Turok - Games
• ATI Radeon HD 4870 X2 - Graphics cards