Intel has unveiled a new express bus and a 3GHz Pentium 4 processor to match, but PC buyers looking for top performance may want to wait and catch a later ride.

Intel's new 875P chipset provides Pentium 4 desktops with an 800MHz frontside bus and dual-channel DDR400 SDRAM main memory. Previously, high-end P4 systems used a 533MHz frontside bus and RDRAM memory.

But performance tests carried out by PC Advisor's sister magazine in the USA, PC World found that the first new systems to use the new processor and chipset show little performance gain in most cases, save for some particularly demanding applications like AutoCAD.

PC World found that while the new Intel components didn't push up the price of the systems it tested, PCs based on AMD's Althon XP 3000+ remain faster and less expensive than the new P4-based computers.

In its tests the top WorldBench score PC World could squeeze from its new P4 systems was 127, which is easily beaten by the score's PC Advisor has been getting from Athlon 3000+ systems, which tops the scale at 138.

In its favour PC World did notice a performance improvement on the old P4 processor and RDRAM combination in its AutoCAD and 3D games tests, but these were the only real areas to benefit.

In May, Intel plans to release similar chipsets, codenamed Springdale, that will allow PC makers to ship 2.8, 2.6, and 2.4GHz P4 PCs with the 800MHz 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 currently isn't in Intel chips slower than 3GHz.

What's the bottom-line buying advice? Power desktop PC users who favour 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 3.4GHz, will double the P4's Level 2 cache and improve the hyperthreading technology. Prescott machines should take fuller advantage of the higher-bandwidth memory and 800MHz bus that the 875P chipset enables.