There are two ways to look at AMD’s new tri-core. The first: Why would I buy a tri core when I can get a quad core? The second (the one that AMD would prefer you use): Why buy a dual when I can get a tri?

That’s the fine line AMD is trying to walk with its tri-core 2.4GHz Phenom X3 8750 proc. It can’t fight Intel’s quads head on, but it’s hoping that people who are considering dual-core procs will see the value in having one more core.

Of course, that was all before Intel slashed prices on its quad-core procs. On April 20, Intel cut the prices of two of its elderly quad cores. The 2.66GHz Core 2 Quad Q6700’s price dropped from $530 to $266 when purchased in bulk. The real trouble for AMD, however, is the 2.4GHz Core 2 Quad Q6600, which took a 16 percent price cut to $224. Just two months ago, the chip was priced at $299. With prices for the Q6600 already dropping to $224, this budget quad core will likely be available for $200 in a few weeks.

With that in mind, we fired up AMD’s X3 on an Asus M3A32-MVP with 2GB of Dominator RAM at 1,066MHz data rates, a 150GB WD Raptor, Windows XP SP2, and a GeForce 9800GX2 GPU. For comparison, we populated a new 45nm Penryn Core 2 Quad Q9300 and a Core 2 Quad Q6600 in an EVGA nForce 790i Ultra motherboard with the same GeForce GX2, WD 150GB Raptor, and Windows XP. The nForce 790i Ultra board features DDR3. Some will argue that the inability to run DDR3 is not Intel’s fault—it’s AMD’s. There is simply no way to run DDR3 on AMD chips right now. And while we could have tested the Intel chips using DDR2, we felt that it wouldn’t be fair to the Intel chips. Instead, we represent the chips on the best platforms available. DDR3, while exotic at the intoxicating high speeds of 1,800MHz and 2,000MHz, is almost affordable at 1,333MHz.

The chip itself should be familiar to AMD fans. It’s a 2.4GHz CPU with the same cache sizes as AMD’s top gun, the 2.5GHz Phenom X4 9850. Each core in the Phenom line features its own 512KB of L2, and all three cores share 2MB of L3 cache. As a 50-series chip, it’s free of the TLB errata that the original Phenoms had. All retail versions of the X3 series will be free of the TLB bug that hurts performance. AMD, however, is selling OEM-only tri-cores that still have the bug.

So how does the tri core stack up? Basically, it’s a quad core with one core turned off. From a practical standpoint, that means it’ll perform right between quads and dual cores. In most games, which generally aren’t optimized for quad cores, it’ll run with the quads. In most encoding applications, including video editing and other quad-optimized applications, it’ll attain roughly 75 percent of the performance of a quad-core Phenom and will definitely be slower than any of Intel’s quads. In other words, it’s not a bad performer in the context of where it’s being wedged.

Price, rather than performance, will probably be the deciding factor for anyone considering an X3. And that’s where AMD has a problem. With Intel putting incredible pricing pressure on AMD these days, the prices for AMD’s processors are incredibly compressed, so it probably doesn’t make sense to buy a tri core. At least not the top-end CPU. AMD’s fastest CPU, the 2.5GHz Phenom X4 9850 costs $235. The new 2.4GHz X3 8705 costs $195. Even more confusing, the 2.2GHz Phenom X4 9550 quad core also costs $195.

Of course, the big question is: What will Intel do in the coming weeks? With its preemptive price cut on the 2.4GHz Core 2 Quad Q6600, the price of that chip at retail outlets drops literally every day we’ve checked this week. If the Q6600 pushes into the $190 range, the X3 doesn’t become competitive until you hit the 2.3GHz Phenom X3 8650 at $165.

This doesn’t factor in overclocking results, as everyone’s mileage will vary with overclocking. We can at least say that AMD’s 50 series B3 cores overclock fairly well. We pushed a 2.5GHz X4 9750 to 3GHz on air cooling, similar results should be expected from the X3s.

There’s also the issue of software compatibility. Fortunately, it’s likely a miniscule problem. However, it’s enough of an issue that AMD decided to inform benchtesters that certain test applications that don’t work correctly with tri cores. Some simply don’t work, while others don’t perform as expected because of sloppy coding that allows them to run on only one, two or four cores.

What should you buy? Ultimately, that’s up to you. If performance is king, you should avoid tri core and go straight to a quad. If you’re on the fence between a dual and a tri, we would take a tri-core Phenom over a dual-core Athlon 64 any day of the week, but up against an Intel Core 2 Duo, it gets a little trickier. We’ll visit that subject in a future story.