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The value proposition
Now that we've buried you under mounds of information, what can we make of it all? One way to filter the information is to consider the value proposition for each CPU model. Exercises like this one are inherently fraught with various, scary dangers—giving the wrong impression, committing bad math, overemphasizing price, coming off as irredeemably cheesy—but our value comparisons have proven to be popular over time, so with the capable assistance of TR System Guide guru Cyril Kowaliski, I've taken another crack at it.

What we've done is mash up all of our performance data in one, big summary value for each processor. The performance data for each benchmark was converted to a percentage using the Pentium 4 670 as the baseline. We've included nearly every benchmark we used in our overall index, with the exception of the purely synthetic tests like Stream. In cases where the benchmarks had multiple components, we used an overall mean rather than including every component score individually. Each benchmark should thus be represented and weighted equally in the final tally. (The one case where we didn't average together a single application's output was WorldBench's two 3ds max tests, since one measures 3D modeling performance and the other rendering.)

This overall performance index makes me a little bit wary, because it's simply a mash-up of results from various tests, rather than an index carefully weighted to express a certain set of priorities. Still, our test suite itself is intended to cover the general desktop PC's usage model, so the index ought to suffice for this exercise.

We then took prices for each CPU from the official Intel and AMD price lists or, in the case of the new Athlon II models, directly from AMD. Since the Phenom II X2 550 isn't on AMD's price page, we took its price from Newegg. For our historical comparison, we've also included the Core 2 Quad Q6600 and the Pentium 4 670 in a couple of places at their initial launch prices.

If we simply take overall performance and divide by price, we get results that look like this:

This bar chart does give us a strong sense of value, no doubt—and the Athlon IIs look excellent in this light—but it may focus our attention a little too exclusively on CPU prices alone. As I've mentioned, for many of us, time is money, and faster computer hardware is relatively inexpensive. What we really want to know is where we can find the best combination of price and performance for our needs. To give us a better visual sense of that, we've devised our nefarious scatter plots.

The faster a processor is, the higher on the chart it will be. The cheaper it is, the closer to the left edge. The better values, then, tend to be closer to the top-left corner of the plot. If you wish, you can find your price range and look for the best performer in that area.

With the data plotted in this fashion, we can see a few other contenders that might join the Athlon II X3 and X4 processors as value stand-outs at higher performance levels, including the Core i5-750, Phenom II X4 965, Core i7-920, and even the Core i7-960. The ghosts of the P4 670 and the Core 2 Quad Q6600 haunt our value scatter plot, as well, reminding us of the dismal CPU values in days past.

That gets us closer to the heart of the matter, but in reality, the price of a processor is just one component of a PC's total cost, and the various platforms do have some price disparities between them. After an epic feud that involved pitchforks, shotguns, and various hurled insults, we finally agreed on some sample systems loosely based on the Utility Player build in our latest system guide for each platform type. Our goal was to achieve rough parity by selecting full-sized ATX motherboards with similar, enthusiast-friendly feature sets. Here are the components we picked for the different platforms, along with system prices:

Platform Total price Motheboard Memory Common components
AMD 790X $608.94 Gigabyte GA-770XT-USB3
($124.99)
4GB Corsair DDR3-1333
($104.99)
XFX Radeon HD 5770 1GB graphics card ($159.99), Western Digital Caviar Black 640GB hard drive ($74.99), Samsung SH-S223L DVD burner (28.99), Antec Sonata III case with 500W PSU ($114.99)
Intel P45 $623.94 Gigabyte GA-EP45T-USB3P
($139.99)
Intel P55 $603.94 Gigabyte GA-P55-USB3
($119.99)
Intel X58 $758.94 Gigabyte GA-X58A-UD3R
($209.99)
6GB Corsair DDR3-1600
($169.99)

What happens when we factor system prices into our value equation?

Whoa. Suddenly, you should buy a Core i5-750! That's more my kind of recommendation. Print this one out and show it to your spouse and/or boss, folks. In the context of a beefy system like this one, going with a cheap CPU like an Athlon II X2 255 or a Pentium E6500 doesn't make a heckuva lot of sense. You'd be paying relatively little more to get substantially higher performance from a faster processor.

Note that, in our main event, the Athlon II X4 635 comes out a little ahead of the Core i3-530, though the contrast between them is fairly minor. Here's the scatter version.

The inclusion of total system prices alters the complexion of our scatter plot somewhat, too, mainly by making the LGA775 and LGA1366 processors look less attractive. The cheaper chips lose their luster, as well. The Core i5-750 and i7-870 remain nicely positioned, while the poorer values include the Core 2 Duo E8600, the Q9400, and the Core i5-661.

Performance per dollar isn't the whole story these days, though. The power efficiency of a processor increasingly helps determine its value proposition for a host of reasons, from total system costs to noise levels to the size of your electric bill. We measured full system power draw and considered efficiency earlier in this article; now, we can factor in system prices to give us a sense of power-efficient performance per dollar.

By this measure, the Core i3-530 is near the top of the charts, and the Athlon II X4 635 is stuck in the middle of the pack—and you should still buy a Core i5-750. The scatter plot tells the story a little differently.

The power efficiency of Intel's newer processors is especially evident here. At system prices around $700, the Core i3-530 is easily superior to the Athlon II X4 635, and at about $800, Intel has three offerings that prove more efficient than the Phenom II X4 965. AMD's dual- and triple-core parts cluster near the bottom corner, cheap but inefficient.