Savor the creamy smoothness
Dual-core processors deliver additional performance in two ways: through the use of multithreaded applications or through improved multitasking. Much of the buzz about the first wave of dual-core processors has centered on better multitasking and the improved user experience that multiprocessing can provide—and rightly so. Dual-processor systems (whether dual CPU or dual core) exhibit a very nice performance characteristic apart from high peak throughput; they don't slow down as easily when things get bad. In a fast, modern PC, avoiding extreme slowdowns—some of which we may not even notice because we've learned to accept them—is a wonderful thing. The move to symmetric multiprocessing on the desktop coincides nicely with the migration of other multitasking-oriented technologies from the workstation/server worlds into desktops, such as RAID and command queuing for storage or the ability to reserve bandwidth for isochronous data transfers. Taken together, these things should allow desktop PCs to deliver a much more responsive experience in difficult scenarios where they have traditionally felt sluggish.

That said, concerns about smoother multitasking will only take us so far. A dual-core CPU like the Pentium XE 840, with its four front-ends thanks to Hyper-Threading, already offers copious amounts of creamy smoothness for multitasking. Adding even more cores in the future probably won't bring many tangible improvements in the user experience. In order for CPU performance truly to continue ramping up over time as it has in the past, thread-level parallelism in software must succeed in delivering real, consistent performance benefits, and not just in easy cases. Some types of tasks lend themselves well to multithreading, but others do not. Currently, virtually no games are multithreaded, for instance, because adding threading complicates development work substantially. Over the long term, the question of thread-level parallelism is the larger one for CPU performance, and that's the issue we've attempted to address in our test selection for this first set of multi-core CPU reviews.

Our focus on thread-level parallelism won't prevent us from savoring the smoothness of dual-core systems, though. We've already hatched plans to test some multitasking scenarios in a future article. If you have any ideas about scenarios you'd like to see tested, feel free to let us know.

These questions about the performance benefits of dual-core processors are magnified by the stark choice presented by the Pentium XE 840. Think about the tradeoff here: you could have a Pentium 4 Extreme Edition with 2MB cache running at 3.73GHz on a 1066MHz front-side bus, or, for the same price, you can get two of the same CPU core with 1MB of cache each running at only 3.2GHz on an 800MHz bus. Which is better? Tough call, but that's the kind of choice Intel's dual-core strategy will present to consumers. We'll keep an eye on that choice as we look through the benchmark results.

Test notes
We've included results for a wide range of CPUs in the following pages, including some workstation-class processors like the Opteron and Xeon. Intel has decided to position the Extreme Edition 840 as a single-socket workstation solution as well as a high-end desktop processor, so these comparisons make some sense. Still, putting the XE 840 up against a pair of Opteron 275s isn't really a fair fight. Those results are included because they shed some light on the question of thread-level parallelism, not because the XE 840 needs to match them.

In fact, the Pentium Extreme Edition 840's most direct competitors here are the Pentium 4 Extreme Edition 3.73GHz, the Athlon 64 FX-55, and the Opteron 175. The FX-55 is AMD's fastest single-core solution, while the P4 XE 3.73GHz is Intel's fastest single-core part. Both are priced comparably to the Pentium XE 840. More intriguingly, the Opteron 175 is AMD's dual-core chip, also priced at $999 along with the XE 840 and the rest. Moreover, the Opteron 175 is essentially the same thing as an Athlon 64 X2 4400+.

We have included results for the Pentium D 840 in our testing, which we obtained by disabling Hyper-Threading on our Extreme Edition 840. Since the Pentium D 840 is just an Extreme Edition 840 sans HT, the numbers should be valid.