The game is changing dramatically, however, with Intel's introduction of its new Core 2 Duo processors and AMD's retaliatory moves. Now, we have some excellent dual-core CPU options that combine solid performance with very low power use at prices around the $200 mark. What's more, because they have relatively modest clock speeds, they may have the potential to overclock like Floyd Landis in Stage 17. From Intel, there's the Core 2 Duo E6300, with 2MB of cache and microarchitectural roots in Intel's mobile products group. From AMD, there's the CPU with the longest name ever, the Athlon 64 X2 3800+ Energy Efficient Small Form Factor. You may use extra energy spitting out that massive moniker, but the chip promises to conserve thanks to its astounding 35W power rating.

We've tested these cool, cheap screamers against a range of today's best processors to see whether one of them might be the right choice for your next PC build. Also, we've taken a little extra time to explore power use, overclocking, and the impact on the Core 2 processors of dropping from 4MB to 2MB of L2 cache. Keep reading to see what we found.

The chips

The first of our two contestants is the Core 2 Duo E6300, the humblest of Intel's new Core 2 processors. Unlike its fancier big brothers, the E6300 has only 2MB of L2 cache to share between its two execution cores. You'll find plenty of sources that will tell you the code name for these 2MB Core 2 Duo processors is "Allendale," but Intel says otherwise. These CPUs are still code-named "Conroe," which makes sense since they're the same physical chips with half of their L2 cache disabled. Intel may well be cooking up a chip code-named Allendale with 2MB of L2 cache natively, but this is not that chip.

Whatever the name, the E6300 shares its faster siblings' 65nm fab process and 1066MHz front-side bus speed, but it runs at a relatively relaxed 1.86GHz clock frequency. The E6300 also has the same 65W thermal design power (TDP) rating as the rest of the desktop Core 2 Duo family, despite its much lower clock rate. The Core 2 Duo E6700, for instance, runs at 2.67GHz and fits into the same 65W thermal envelope. In practice, I would expect most Core 2 Duo E6300s to use less power than an E6700, although power use will vary from chip to chip because Intel sets stock voltages for each processor at the factory.

Regardless, the Core 2 Duo line's 65W TDP compares quite favorably to the Pentium D 805's 95W rating or the Pentium D 950's considerable 130W TDP.

If you really want to go low on the power, though, our second contender may be an even better fit. AMD uses a more conservative formula to estimate thermal design power than Intel, and even so, the Athlon 64 X2 3800+ Energy Efficient Small Form Factor carries a TDP rating of only 35W. As you might have gathered, this puppy is intended for use in low-power, low-noise systems such as home theater PCs.

In fact, we should come clean. Our efforts to compare this processor to the Core 2 Duo E6300 may not be entirely apt. AMD offers two other versions of the Athlon 64 X2 3800+ for its Socket AM2 infrastructure that might be a closer match for the E6300. The plain ol' Athlon 64 X2 3800+ comes with a TDP of 89W, while the Energy Efficient (but not Small Form Factor) version has a 65W TDP. AMD makes these different power grades of its processors by tweaking the way that the chips are fabricated, and it charges more for the lower power versions.

Heck, the, err, A64 X2 3800+ EE SFF is almost certainly the same chip as the Turion 64 X2, but with different packaging and pinout. It's possible that Intel might eventually release a similar low-power version of the Core 2 Duo that's based on the "Merom" mobile variant of the Core 2.

Fortunately, the performance of all three flavors of the Athlon 64 X2 3800+ products should be virtually identical, so our performance numbers should be relevant for any of them. All three are 90nm chips that run at 2GHz with 512KB of L2 cache per core.

The new math
Back when we reviewed the high-end versions of the Core 2, AMD had pledged to cut prices to maintain a price-performance ratio similar to Intel's, but we didn't yet know exactly how those prices would look. Now the price cuts have come, and they're deep. Here's how things stack up.

Intel's introductory prices for the Core 2 were very reasonable, and AMD really took the axe to its price structure in response. For our purposes, though, these price lists are a little bit iffy. The E6300, for example, is selling at online vendors for between $220 and $230, well above its $183 list price, probably because supply of these chips is still spotty. Meanwhile, the price of the Athlon 64 X2 3800+ EE SFF is not listed at AMD's website, and the chips themselves aren't yet showing up at online retailers. AMD says initial supplies of the EE SFF were all snapped up by a major PC manufacturer, but it expects to see processors selling individually by later this month. When that happens, I wouldn't be surprised to see the EE SFF end up in the same $220-230 range as the Core 2 Duo E6300.