Amid the spectacle of wardrobe malfunctions and abnormally large caches, some noteworthy developments got a little lost. For one, the new Prescott processor was a shockingly major replumbing of the familiar Pentium 4, with an uber-deep 31-stage pipeline and a host of internal tweaks. These changes made Prescott usually a little slower, clock for clock, than the previous Pentium 4. What's more, Intel was launching a pair of products, the Pentium 4 3.4GHz and 3.4'E' GHz processors, that didn't appear to exist yet. We were testing old and new Pentium 4 cores, Northwood and Prescott, at 3.2GHz, but not beyond. Only the P4 Extreme Edition was available for review at 3.4GHz.
The fact that samples weren't available to the press was a bad omen. Over the ensuing days and weeks, it became clear Prescott supplies were tight at any speed. However, about three weeks ago, Intel made good on its promise to follow up with samples of its Pentium 4 3.4GHz chips when they became available. Today, at last, we can show you how they perform.
If you aren't familiar with the new Pentium 4 Prescott processor core, you really should go read our initial review of it. The changes from the older Northwood core are too complex to summarize easily. That said, I'll make a feeble attempt. Prescott includes larger caches, a much deeper main pipeline, SSE3 instructions, improved data prefetching, revised Hyper-Threading, and enough microarchitectural tweaks to kill a horse. Most importantly, Prescott is manufactured using Intel's new 90nm fabrication process, making it a smaller chip than the 130nm Northwood, despite having a much higher transistor count.
Generally, the deeper we get into the technical stuff, the happier I am. However, I'm none too excited about making these articles difficult to read. So, as you peruse the following pages and glance over test results for no less than eighteen different CPUs, please keep a few things in mind.
First, Intel distinguishes the new Prescott Pentium 4 from the regular ol' Northood P4 by tacking an "E" on to the end of the name, after the clock speed. So when you're reading our graphs and see a Pentium 4 "E" processor, think Prescott. The Pentium 4 "C" you'll see here is simply a Northwood chip. It gets the "C" tag because it has an 800MHz bus, while older versions of that chip did not. (All the Pentium 4s we've tested here have an 800MHz bus.) Forgive the confusion, but we've tried to stick to Intel's naming scheme where possible, and confusion may be the natural outcome of that effort.
Next, you may recall from our original Prescott review that we actually published a complete set of benchmark results for the Northwood 3.4GHz processor way back then. We accomplished this feat by disabling the L3 cache on our Pentium 4 Extreme Edition 3.4GHz processor, effectively making it a Pentium 4 Northwood running at 3.4GHz. We've used the actual Northwood 3.4GHz to verify that our "simulated" Northwood 3.4GHz results were correct, but we didn't rerun every test, because we're confident our results are representative.
Finally, watch the line graphs that come after our usual bar graphs to see how each CPU type scales with clock speeds or model number increments. We will be keeping an eye on Northwood versus Prescott in particular, because that's a key issue. We're wondering whether Prescott performance gets relatively stronger as clock speeds go up, because Prescott is intended to run at high clock frequencies. In fact, it's slated to hit 4GHz or so by year's end, while Northwood will be phased out.