Conclusion

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The results of our tests are somewhat ambiguous, so let's first summarize the pros and cons:

Pro AMD Quad FX:

Very sophisticated, state-of-the art 32/64-bit uber-enthusiast platform
Huge bandwidth between processor(s) and northbridges
Dedicated main memory for each processor
Works with mainstream DDR2-800 memory
Dual-processor system very likely to scale better under Windows Vista Ultimate Edition
Entry-level Athlon 64 FX-70 twin-processor kits available at $599
Dual-socket platform allows for future upgrade to quad core processors (eight cores per system)

Contra AMD Quad FX:

Very high power requirements due to two processors
High cooling requirements (air conditioning?)
Power draw of 500+ W requires at least a 750 W power supply
Very high platform costs (four memory modules and a $400+ motherboard)
Platform benefits not noticeable with most of today's applications
Virtually no overclocking margins for the FX-74 top model
Only a single motherboard available (Asus); likely not available in retail, but via system integrators

Although the primary goal of releasing a workstation-type enthusiast PC for the desktop might have been to answer Intel's quad core offering, AMD has invested a lot in the platform. No other solution offers the bandwidth reserves of a Quad FX, and no other solutions promise such a predictable upgrade. As soon as AMD's "Agena FX" quad cores become available next year you'll be able to replace today's FX-70 series processors and substantially increase your computing power. So, clearly, the platform is brilliant from a technology standpoint.

Unfortunately, considering the effort required to bring this platform into life, the results aren't terribly impressive in terms of both performance and performance per watt. Why should I buy a pair of processors, an expensive and very special motherboard and a heavy duty 1,000 W power supply when I can get almost the same experience with much cheaper mainstream components and Intel's quad core processor? Sure, I won't be able to upgrade an Intel machine to eight cores by the middle of 2007, but AMD's Quad FX powerhouse will be outdated by that time as well. HyperTransport 3.0, with double the clock speed, is waiting for its spring debut, and although the quad core Agena FX will run in today's Quad FX systems, it will have to live with standard HT link speeds.

We still see one reason to go for Quad FX right away: if your ego can live with the FX-70 entry-level model, you will have to pay only a somewhat reasonable $599. Most likely you'll be able to overclock the CPUs to at least 2.8 GHz, likely even to 2.9 or 3.0 GHz, by increasing the base clock speed. If so, you'll get kick-butt performance for a very acceptable price, considering that Intel's Core 2 Extreme QX6700 is still at $999. All you have to decide is whether or not you want to hunt down one of the L1N64-SLI WS motherboards from Asus.

Another possible reason to go for Quad FX instead of Core 2 Quad is the supposedly better scalability of the former under Windows Vista Ultimate Edition. The top version of Microsoft's new operating system will be smarter when it comes to multi-threading and multi-tasking, which could favor AMD's new uber-platform. But again, we cannot say we're particularly convinced that we should spend a lot of money on a motherboard and expectedly $400 on Vista Ultimate in January.

The bottom line is obvious: Quad FX is hot, but its time has not yet come.