As far as we can see it, there are four different factors that go into the purchasing decision of one of these next-gen platforms.
The first is price. AMD has the upper hand here. Although its Phenom II X4 940 is priced fairly close to Intel’s Core i7 920, 790GX-based motherboards cost in the neighborhood of $150, while high-end X58 platforms generally tend toward $300 (although we’ve recommended a $250 model here). DDR3 memory is still significantly more expensive than DDR2. Populating three channels, the more modern technology is going to bear a notable premium over two channels of the more mainstream type. In all, the Phenom II machine costs about $250 less to build than our i7 box did, while arming the AMD platform with a better aftermarket cooler would have shaved $50 or so from its advantage.
Next is performance. Intel maintains its advantage in this one, even with both configurations overclocked. We very effortlessly achieved a 3.8 GHz overclock on the i7 920 by bumping its Bclk up to 190 MHz and keeping all other settings in place. Knowing that our own German lab was able to reach 3.8 GHz stably on air (and AMD’s lab team said to expect frequencies up to 3.9 GHz at 1.55 V), we pushed our X4 940 extremely hard. While we were able to boot at up to 3.8 GHz, benchmarks wouldn’t finish consistently until we had dropped down to 3.64 GHz—and that was still at 1.6 V. Anything less and even that speed wasn’t 100% solid. Given the speeds we were able to achieve, Intel’s entry-level Core i7 walked away from AMD’s fastest Phenom II in every single one of our tests.
Third, you have power. We’re giving this one to AMD, as well. At idle—where you’ll spend most of your time—the overclocked Phenom II spins down to 800 MHz and yields some impressive power figures. Once it shoots back up to 3.64 GHz, it’s sucking down more juice than Intel’s 3.8 GHz Core i7. However, we anticipate that most enthusiasts aren’t going to peg their chips at redline very often.
Finally, there’s the upgrade question. For owners of existing Socket AM2+ motherboards, today’s Phenom II is a drop-in component. Provided that your board and graphics are beefy enough to warrant the new CPU, stepping up is a matter of spending $275. Conversely, adopting i7 means buying a CPU, motherboard, and DDR3 memory, at least. This isn’t necessarily a bad thing. Intel has always been aggressive about nudging the bleeding edge forward and advocating new technologies—sometimes to its own detriment. We know DDR3 is going to replace DDR2, and it’s nice to have an X58 board able to support CrossFireX and SLI. AMD’s upgrade path simply lets enthusiasts stretch their aging hardware out a little bit longer.
So What Do I Buy?
The Core i7 and Phenom II seem suited to two different customers. Indeed, there will undoubtedly be gamers who go all-AMD and are willing to sacrifice a bit of speed in order to save money and Intel loyalists who adopt i7 at a bit of extra cost for its newer technology. We thus see distinct advantages to each platform.
For the gamer or multimedia aficionado with a mind to performance, Intel’s Core i7 920 overclocked to 3.8 GHz simply delivers the most compelling experience. The ~$250 hardware price premium is the cost of entry over AMD’s solution, and we think it’s worth paying. AMD is planning its own shift to DDR3 in the first half of 2009, and less-expensive X58 boards are trickling out (the cheapest right now being Gigabyte's $210 EX58-UD3R), so the cost-difference will continue getting smaller.
If you’re instead buying for a more productivity-oriented purpose, the Phenom II makes sense. After all, it’s able to handle every task nearly as well as i7 does (both platforms overclocked, of course), it drops into existing AM2+ motherboards, it costs less, and in a majority of situations, will use substantially less power—even highly-tuned, as we've done here. We didn’t have as much luck overclocking the Phenom II as we expected, but the chip is still a notable improvement over AMD’s 65 nm Phenom series.