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The value proposition
We've taken a long and meandering route through several truckloads of performance data, and in order to help you make sense of it all, we have ripped a page from our last CPU value article.

To create a synthetic "overall performance" score, we computed an unweighted average of the results for a subset of our tests consisting of the benchmarks used in the CPU value article. Our formula includes 22 different benchmarks, but since our aim is practicality, it excludes a few more esoteric ones like the scientific computing applications. As our baseline, the Athlon X2 6400+ gets a 100% score. Other scores are all relative to it.

Of course, what you see below is a crazy experiment and probably meaningless, but some folks may find it a worthwhile thought exercise, at least. These scatter plots show price versus performance in a fairly intuitive way. To oversimplify slightly, the best CPU values tend to be located closer to the top and left edges of the plot.

As one might expect, some of the new CPUs we're reviewing today come out looking good in this analysis. The totality of our benchmarks is somewhat biased toward multi-core processors, so the Core 2 Quad Q8400 shows up in a nice spot on this plot—as does its rival, the Phenom II X4 940, whose overall performance is slightly higher. The Pentium E6300 appears to have a clear edge over the Athlon II X2 250, but the Phenom II X2 550 is also a strong value with a higher performance rating.

Of course, the 975 Extreme is no great value, but it is progress over the like-priced Core i7-965, which it replaces.

Now, here's another crack at the same issue with total system cost taken into account. To get our pricing numbers for the X axis, we've added the cost of a motherboard, memory kit, graphics card, and hard drive to that of our processors. Wherever it made sense, we picked components from our latest system guide. Also, we got all our prices from Newegg. Here's a complete breakdown:

Intel LGA775 platform AMD Socket AM2+ platform Intel Core i7 platform
Gigabyte GA-EP45-UD3P $135 Gigabyte GA-MA790X-UD4P $110 Gigabyte GA-EX58-UD3R $200
4GB Kingston DDR2-800 $51 4GB Kingston DDR2-800 $51 6GB Corsair DDR3-1600 $104
Sapphire Radeon HD 4870 512MB $165 Sapphire Radeon HD 4870 512MB $165 Sapphire Radeon HD 4870 512MB $165
Western Digital Caviar Black 640GB $75 Western Digital Caviar Black 640GB $75 Western Digital Caviar Black 640GB $75
$426 $401 $544

Notice that we are making some assumptions here that may not be entirely valid. For instance, we've priced the Socket AM3 Phenom II processors on a Socket AM2+ motherboard with DDR2 memory, though we tested most of them with DDR3 memory. As you may have noticed, memory type didn't make much difference at all to the performance of the Phenom II X4 810, and we expect the story will be similar for the rest. In the same vein, we priced the Core 2 processors with DDR2 memory, though we tested them with DDR3. Our goal in selecting these components was to settle on a standard platform for each CPU type with a decent price-performance ratio, not to exactly replicate our sometimes-exotic test systems.

Thanks to a lower overall cost for the Socket AM2+ platform, the AMD processors separate themselves from the Intels in this plot. Rather dramatically, a line of green dots runs down the left edge of the performance results between 100% and 175%. Assuming this difference in motherboard prices holds up as typical in the market, the Athlon II and Phenom II chips at various price points look to be the better deals, generally. Among the strongest values from Intel are the Core 2 Quad Q8400 and the Core i7-920, which is in a class by itself.

For what it's worth, the Core i7-950 would presumably sit atop the i7-940 just like the i7-975 does above the i7-965 at the same price point, as a slightly better value.