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Intel is unveiling this week a new express bus and a 3-GHz Pentium 4 CPU to match, but PC buyers looking for top performance may want to wait and catch a later ride.

Intel's new 875P chip set provides Pentium 4 desktops with an 800-MHz frontside bus and dual-channel DDR-400 SDRAM main memory. Previously, high-end P4 systems used a 533-MHz frontside bus and RDRAM memory. However, PC World Labs tests of three of the first new systems show little performance gain in most cases, save some very demanding applications like AutoCAD.

Although you won't see any additional price premiums for systems with the new chip set, Athlon XP 3000+ systems from rival Advanced Micro Devices remain faster, on average, and less expensive than the new P4 PCs. And if you're an Intel devotee, there's another reason to hold off: A big P4 improvement awaits you in June.

Shortly after its announcement Monday, Intel said it is delaying shipment of the new 3-GHz P4 chips after discovering an unspecified anomaly. The company says the issue does not affect the new chip set.

An 800-MHz Gimmick?

Just what's the deal with Intel's new 800-MHz bus? It's a marketing tool, for now, but helps Intel prepare for the future, says Kevin Krewell, general manager at research firm In-Stat/MDR. Most of today's software doesn't push the P4 CPU hard enough to require this bus.

"The extra bandwidth is probably overkill for most applications," Krewell says. The older 533-MHz bus supported a maximum throughput of 4.2GB per second, while the 800-MHz one tops out at 6.4 GBps.

That certainly seems true in PC WorldBench 4 tests of three preproduction 3-GHz P4 systems with the new 875P chipset: the $2999 Dell Dimension 8300, $3179 Gateway 700XL, and $3845 Falcon Northwest Mach V, all with 1GB of DDR-400 SDRAM. For comparison, the tests included a similarly configured Falcon Northwest Mach V system with the 3.06-GHz Pentium 4, 533-MHz frontside bus, and 1GB of PC1066 RDRAM.

Though the Falcon system with the 800-MHz bus completed PC WorldBench 4 tests fastest with a score of 127, the comparison Falcon unit was only two points lower, and three previously tested 3.06-GHz P4 PCs with PC1066 RDRAM averaged 121. These differences are too small for you to notice with productivity applications.

Plus for Graphics

The 800-MHz bus and DDR-400 memory did produce a noticeable speedup in two tests that really push system and memory strength, however: the AutoCAD test and the Return to Castle Wolfenstein and Unreal Tournament games. The newer Falcon unit zipped through the AutoCAD test in 256 seconds, compared to 265 seconds for the comparison Falcon system. The Dell did even better, finishing in 253 seconds. In Return to Castle Wolfenstein, the 800-MHz bus Falcon PC zoomed along at 122 frames per second, compared to 115 frames per second for the comparison unit. (All machines used a top-notch ATI Radeon graphics card.)

In most other tests, we saw little noticeable difference with the new bus.

Overall, AMD Athlon XP 3000+ systems still come out on top on PC WorldBench 4, with three previously tested PCs averaging a score of 136. They complete the AutoCad test in an average of 226 seconds and the Premiere tests in an average of 210 seconds--a significant improvement over the P4 machines. The new Intel units hold a noticeable lead only on the two games and the Musicmatch test.

On value, the Dell and Gateway prices fall in line with what might be expected for well-loaded systems with the current top P4 setup. But the Falcon unit seems pricey, even considering it's an enthusiast model with an aluminum case, RAID 0 setup with two 36GB hard drives, a DVD-RW drive, top-notch Monsoon Planar Media 14 2.1 speakers, and a 17-inch monitor. A similarly configured Falcon unit with the AMD Athlon XP 3000+ CPU will save you $150.

Buying Strategy

There's a bit more to the 875P chipset than bus and memory improvements. It also builds in support for gigabit Ethernet, Serial ATA hard drives, and software support for two-hard-drive RAID setups. What's missing? Support for RDRAM, which is Rambus memory. Intel is moving away from this pricey, controversial memory in favor of DDR.

In May, Intel plans to release similar chip sets, code-named Springdale, that will allow PC makers to ship 2.8-, 2.6-, and 2.4-GHz P4 PCs with the 800-MHz bus and DDR, analysts say. These systems for budget-minded businesses and consumers will also feature improved integrated Intel graphics and hyperthreading, the CPU technology designed to improve multitasking. Hyperthreading isn't in Intel chips slower than 3 GHz.

What's the bottom-line buying advice? Power desktop PC users who favor Intel-based machines may want to sit tight until June. That's the expected debut date for "Prescott," the revamped P4 chip for which the 875P chipset paves the way. Note, too, that you can upgrade PCs with the 875P chip set to Prescott later if you need to buy an Intel system now.

Prescott, likely to launch at a 3.4-GHz clock speed, will double the P4's Level 2 cache and improve the hyperthreading technology. And, Prescott machines should more fully take advantage of the higher-bandwidth memory and 800-MHz bus that the 875P chip set enables, Krewell says.

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• Dell Dimension 8300 Gateway 700XL,
• Falcon Northwest Mach V