Why I am a bad person
This is the part of the review where I explain why I benchmarked what I did, the way I did, and in such obvious violation of the Sacred Creed of Geeks Everywhere.

First, I tried to test the CPUs in such way as to show their benefits and limitations. To do so, I used the brand-spanking-new Windows XP x64 Edition operating system and a number of 64-bit applications. WinXP x64 is NUMA aware—that is, it comprehends the need to put data into the memory attached to the CPU modifying that data. By nature, Opteron systems require a NUMA-aware OS in order to perform at their best. Also, AMD says that the WinXP x64 scheduler is especially well tuned for dual-core processors.

Obviously, 64-bit applications are the future of dual-core processors. All of the CPUs that I tested, including the moldy old Opterons, newer Xeons, and brand-new dual-core processors from AMD and Intel, are 64-bit capable. I also tried to make use of multithreaded applications where possible, although some programs aren't threaded and some types of tasks simply don't lend themselves to multithreading. The end result is that nine of our 15 test applications are multithreaded, and of those nine, five are 64-bit binaries.

I understand that multitasking has been cited as one of the key areas where dual-core processors will benefit the end user, and I certainly don't disagree entirely. The full-fat, Atkins-approved creamy smoothness that comes with a multiprocessor system will be a boon in desktop systems and in low-end, single-processor workstations, and I have extolled its virtues at length in the past. However, most workstation-class systems are already multiprocessor boxes. Not only that, but we are living right now in what I'd call the Multitasking Moment, as we transition from one CPU core to two. Once dual-core processors become more common, multitasking smoothness will no longer be a big issue. The more relevant question as we move to two, four, eight, and more CPU cores per system will be about the benefits of thread-level parallelism to outright performance, and that is the question I've attempted to address in my testing.

I also have not made any attempt at server-class testing in this review. I would have loved to do it, but it would be a new enterprise for us around here, and we had our hands full in doing the testing we did. I would also like to apologize for the workstation purists for not ponying up the cash for high-end Quadro or FireGL graphics cards for our test systems. Truth be told, I would have loved to use them, but the dual Xeon rig soaked up our budget for this review. And that's without us paying through the nose for registered DDR2-400 DIMMs for that rig. I am, as I said, a bad person.

I am also probably a bad person for focusing primarily on DCC and scientific computing instead of CAD/CAM applications that are generally not multithreaded. Even worse, I threw in a few game benchmarks at the end of the review. Please, whatever you do, don't tell your boss about those.

I am also a bad person because I really like Tyan's wicked S2895 motherboard that
sports dual 940-pin sockets and dual 16-lane PCI-E x16 slots.

Cool stuff to watch for in the results
There are a number of intriguing matchups in our benchmark results. Let me outline a few of them, so you know what to watch for.

• Opteron 175 versus dual Opteron 248 — This is a matchup at 2.2GHz between a dual-core Opteron and a pair of single-core Opterons. Is it better to have two cores situated closely together, or is having double the memory bandwidth, as the Opteron 248s do, preferable?

• Opteron 175 versus Opteron 152 — So would you rather have: a single-core Opteron at 2.6GHz or a dual-core model at 2.2GHz?

• Dual Opteron 275 versus dual Xeon 3.4GHz — Yes, Intel has newer Xeons out with 2MB of L2 cache, but we couldn't find them to purchase when we were buying hardware for this review. We suspect that cache size doesn't make much difference in most of the applications we're testing, which don't tend to use the extra meg of cache very well. (See our P4 600 series review for more on the 2MB cache's performance impact.) The question is, how does a dual-CPU Hyper-Threaded Xeon compare to a quad-core Opteron?

• Opteron 175 versus Pentium Extreme Edition 840 — Dual-core processors from AMD and Intel go head to head. Perhaps we're crossing market segments a little bit here, but then Intel targets its high-end Pentium chipsets and processors at the low-end workstation market. The Opteron 175 and Extreme Edition 840 are arguably direct competitors. Who else is Intel targeting with a pair of 3.2GHz Prescott cores on one chip?

  Evil people who wish to observe possible desktop processor performance matchups should note that the Opteron 175 is essentially identical to the Athlon 64 X2 4400+.

• Dual Xeon 3.2GHz versus Pentium Extreme Edition 840 — Both are dual Prescott cores with 1M of L2 cache running at 3.2GHz on a shared 800MHz front-side bus. The Xeon is saddled with a slower memory subsystem, while the Pentium XE 840 is one chip rather than two. Hmm.

• Pentium Extreme Edition 840 versus Pentium D 840 — If you disable Hyper-Threading on the Pentium XE 840, you get a Pentium D 840. That's exactly what we did, because we were curious to see the performance impact.

• Redemption for Prescott? — We've used a mix of single-threaded and multithreaded applications in our past CPU reviews, but we're using more threading now than ever. Does Intel's Hyper-Threaded processor core regain some of its luster when more of the benchmarks go multithreaded?

• Dual Opteron 275 versus the world — What can a dual-socket, quad-core system do better than any of the two-core systems we're testing here? Not everything, because some applications only spin off one or two threads. In some cases, though, well, you'll see..