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Today's processors: the value angle

When performance meets price, round two
— 12:43 PM on May 27, 2008

Almost a year has passed since our first CPU value article. Since then, we've taken a look at the value propositions of current graphics processors, but we haven't taken another shot at CPUs—until today, that is. Fresh from our review of AMD's triple-core Phenom X3 processors, we've gathered all of our benchmark results and tossed current official pricing into the equation to see how much bang Intel's and AMD's latest processors deliver for your buck.

In this look at the CPU market, we explore how value scales across two, three, and four cores, whether bargain prices make AMD's Phenoms attractive from a value perspective, and how Intel's blazing-fast dual-core CPUs like the Core 2 Duo E8400 fit into the picture. Our results span 20 processors, 18 different benchmarks, and some custom tests that take power efficiency and more complete system pricing into account. Keep reading to see where the best values lie in the CPU market.

Quantifying CPU value
We noted in our GPU value article that it's much easier to calculate value with microprocessors than with graphics processors. That's true, but CPU value isn't a completely straightforward affair either. We have two main variables to work with—performance and price—so working out a "performance per dollar" figure is easy enough. However, that equation doesn't take into account a wealth of other performance factors, including memory bandwidth, storage bottlenecks, and graphics processing power in games. Power consumption also plays an important role, especially when it comes to the cost of a cooling solution. We'll focus on CPU performance-per-dollar almost exclusively in this article, but while reading, keep in mind that there are other factors to take into account.

With that out of the way, let's look at our test subjects. We have 20 processor configurations, 11 of which bear the Intel logo:

Model Clock speed Cores L2 cache (total) Fab process TDP Price
Core 2 Duo E7200 2.53GHz 2 3MB 45nm 65W $133
Core 2 Duo E6750 2.66GHz 2 4MB 65nm 65W $183
Core 2 Duo E8400 3GHz 2 6MB 45nm 65W $183
Core 2 Quad Q6600 2.4GHz 4 8MB 65nm 95W $224
Core 2 Duo E8500 3.16GHz 2 6MB 45nm 65W $266
Core 2 Quad Q9300 2.5GHz 4 6MB 45nm 95W $266
Core 2 Quad Q9450 2.66GHz 4 12MB 45nm 95W $316
Core 2 Extreme QX6850 3GHz 4 8MB 65nm 130W $999
Core 2 Extreme QX9650 3GHz 4 12MB 45nm 130W $999
Core 2 Extreme QX9770 3.2GHz 4 12MB 45nm 136W $1399
Dual Core 2 Extreme QX9775 3.2GHz 8 24MB 45nm 300W $2998

The other nine chips come from AMD:

Model Clock speed Cores L2 Cache/L3 cache Fab process TDP Price
Athlon X2 5600+ 2.8GHz 2 1MB 90nm 80W $122
Phenom X3 8450 2.1GHz 3 1.5MB/2MB 65nm 95W $145
Athlon X2 6000+ 3GHz 2 1MB 90nm 125W $153
Athlon X2 6400+ 3.2GHz 2 1MB 90nm 125W $163
Phenom X3 8750 2.4GHz 3 1.5MB/2MB 65nm 95W $195
Phenom X4 9500 2.2GHz 4 2MB/2MB 65nm 95W $195
Phenom X4 9600 2.3GHz 4 2MB/2MB 65nm 95W $215
Phenom X4 9750 2.4GHz 4 2MB/2MB 65nm 125W $215
Phenom X4 9850 2.5GHz 4 2MB/2MB 65nm 125W $235

As in our last CPU value piece, we've taken bulk prices straight from Intel and AMD. Volume prices aren't always representative of what consumers pay, but the two are close enough right now, and selecting "official" figures saves us the trouble of working out averages from fickle online retailers. Again, there are other factors to take into account here, such as platform and power costs. We'll look at how platform pricing fits into all this soon, but let's focus on just the processors for now.

Oh, also, we've included AMD's Phenom 9500 and 9600 processors in our tests. These two chips are plagued by the infamous TLB erratum, the fix for which (enabled in most BIOSes by default, we might add), hurts performance significantly. We've disabled the fix for our tests, so our results should roughly represent the performance of the new, erratum-free 9550 and 9650 CPUs. We nevertheless resisted the temptation to simply rename our test chips, because the 9550 and 9650 are based on a new stepping of silicon and may perform slightly differently.

To paint a reasonably thorough picture of how all these processors handle common tasks, we've selected 18 benchmarks spanning everything from games, general productivity applications, and media encoding to folding, 3D rendering, and game development. The vast majority of these tests cover real-world applications, which we think is fitting considering the practical aim of this article.

Organizing all this data in a readable fashion isn't an easy enterprise, so we've relied on a mix of charts and scatter plots once again. For each benchmark, we'll start with a look at raw performance, then move on to a bar chart that ranks chips based on how much performance they deliver per dollar. When we're dealing with tests that generate higher scores with faster CPUs, we'll look at "score point per dollar." However, when the performance metric shifts to time in seconds, where lower scores represent better performance, we'll rank chips based on test run rate per dollar. The test run rate will be the reciprocal of the test score, expressed in megahertz.

The third tool we use quantify value is our trusty scatter plot:

Those who've checked out our previous two value articles will know the drill. The best possible chip would be at the top left, costing nothing while delivering maximum performance, while the worst would be at the bottom right, offering the lowest performance at the highest cost.

There's a twist here, though. Since we have lots of chips, and our two-way Core 2 Extreme QX9775 would prolong the X axis substantially due to its high price, we've made two compromises in order to keep our scatter plots readable. For one, you won't find the QX9775 setup listed at all in our scatter plots. This isn't much of a sacrifice, since the priciest configuration almost always offers the worst value. The second compromise involves cropping the bottom of our Y axis. In the plot above, for example, the Y scale starts at 2000 instead of zero. We prefer to maintain a proper scale for our graphs here at TR, but in this case, we've elected to err on the side of readability. The scatter plots are a little tricky to decipher as it is, and without cropping, all our results would often be squeezed into roughly two square inches of graph area.

Let's now have a brief look at our test systems and, after that, our results.