When Intel launched its 64bit Pentium 4 and Pentium 4 Extreme Edition desktop processors in February, it gave the 64bit computing future that started with AMD's Athlon 64 chips even more traction, and finally some sort of competition.

What does 64-bit computing offer you beyond today's 32-bit platform? We have compared two of the new chips, the 3.73GHz P4 EE and the 3.6GHz P4 660, with a 32bit 3.8GHz P4 (the fastest 32bit P4), a 2.6GHz Athlon 64 FX-55 and a 2.4GHz Athlon 64 3800+.

Results were mixed: the new 64bit P4s gave a slight boost over a 32bit P4, but you will pay a price premium for an Intel PC over an AMD one with similar or slightly better performance.

Intel also has implemented its 64bit extensions on P4 chips at 3GHz to 3.4GHz, and will do so on forthcoming P4 and Celeron CPUs. The new P4s also get a boost in their on-board L2 memory cache from 1MB to 2MB.

You won't need a new motherboard for the new chips, but to get the most out of their 64bit capabilities, you will need to upgrade your BIOS and, of course, run a 64bit operating system.

Microsoft's 64bit Windows XP Professional X64 should be generally available in late April; it will run on PCs using both Intel's and AMD's 64bit chips. Systems with 64bit P4 and P4 EE CPUs are already on sale.

We tested the 64bit processors with both 32bit Windows XP Professional and Release Candidate 2 of Windows XP Pro X64; the 32bit P4 was tested only with standard Windows XP Pro.

The Athlon 64 3800+ and the 3.6GHz Pentium 4 scored so close to one another on WorldBench 5 under 32bit Windows that users wouldn't notice a difference. The gap was slightly more noticeable between the Athlon 64 FX-55 and the P4 EE, but still under 10 percent.

Until XP Pro X64 ships, most users – save those running Linux, which can already take advantage of 64bit CPUs – won't derive any benefits from 64bit computing. Even when the operating system ships, only applications optimised and recompiled to take advantage of the new capabilities will deliver any performance increase.

Note also that the main boon of 64 bits is the ability to handle larger amounts of data and at higher resolutions, not speed. That means a 64-bit PC will be able to juggle far larger databases and spreadsheets, a lot more on-board memory (up to 64GB with Intel's 64-bit solution and 1TB (terabyte) with AMD's version), and higher resolution in games, audio and video, but it will not give huge performance boosts.

A couple of other caveats before you jump the 32bit ship: 32bit drivers don't work with Windows XP Pro X64, and vendor support for older hardware will probably be skimpy. Companies are reluctant to spend money updating drivers for products they no longer sell. If you want to hold on to older hardware, you might have better luck with 64bit Linux since there's often someone, somewhere who will take the time to write drivers for legacy equipment.