Phenom II: AMD pulls closer

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Can you re-use your AM2/AM2+ motherboard when upgrading to a X4 920/940? If you know that your board is limited to 95W processors, you're probably out of luck. If it's not, then check with your manufacturer to see if it's already listed as compatible — a BIOS update will definitely be required. If you can't find any information, hang tight, the majority of AM2+ boards should be compatible, even ones that use older chipsets like AMD 690G. It's simply a matter of waiting for the manufacturers to get their acts together.

Our motherboard sample was flashed by AMD before we received it, but don't expect boards to compatible out-of-the-box, not even high-end models. It may be a little while before boards start shipping with a compatible BIOS; check with the manufacturer before buying. For compatible AM2 boards, note that the CPU will run at a lower HyperTransport speed, which may affect performance.

Also to be considered is what AMD has coming up next, AM3, which we may see as early as next month. The AM3 socket will not be compatible with AM2/AM2+ processors because they lack DDR3 memory controllers. Phenom II for AM3 will be backward compatible with AM2/AM2+ boards however. DDR3 will no doubt bring further performance increases, but even if you decide to stick with AM2+ and DDR2, it may be prudent to wait for AM3 Phenom II's, as they will give you an upgrade path to AM3 in the future.


The power consumption of our X4 940 test system was misleading. While it generated an equivalent idle power draw to the Core i7 system, and bested it by 10W during full load, when actual work needed to be done, i.e. our real-world application test suite, the Phenom II took longer to complete each task and used more power doing so. We find the same is true when comparing AMD Athlon X2 processors to Intel Core 2 Duos.

The X4 940's overall performance was mixed, nearly matching an equivalently priced Core i7 in some tests, while falling significantly behind in others. It is probably more suited to compete with older Core 2 Quads. For a wider scope of how the X4 940 performs, we suggest you look at the myriad of benchmarks that will be available at sites such as The Tech Report, Anandtech, and X-bit Labs.

From a purely financial point of view, Phenom II is an attractive option compared to Core i7. Motherboards (many with IGPs included), memory, and heatsinks — they're all much cheaper for Phenom II. When all the component prices are added up the difference between a Phenom II system and one based on i7 920 will easily exceed $200. For gaming, graphics cards are typically the weakest link in the chain, so an extra $200 for that can be substantially more beneficial than having a faster CPU. Phenom II also overclocks well, closely matching the i7 parts in this regard.

AMD might not have closed the gap with Intel yet, but we're to happy to see that a high-end AMD machine is actually a viable option again, and not just an exercise in fanboy love. The processor wars continue, and consumers will benefit for some time to come.

Our thanks to AMD and Gigabyte for the CPU and motherboard samples.

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Articles of Related Interest
Intel Core i7: Nehalem Launched
Core i7 News
Intel Developers Forum, Fall 2008
Desktop CPU Power Survey, April 2006

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