A curious thing is happening in the processor business. Although AMD's Phenom hasn't exactly taken the fight back to Intel in the benchmarks, its numbering system is strangely easy to mix up with the latest generation of Intel quad-cores. Both are called 9000 series.

Just to obscure things even more, it looks like the triple-core Phenom will be the 8000 series - the same as the 45nm Wolfdale Core 2 Duo. Those of us who keep a close eye on the processor business will know the difference between an Intel Core 2 Duo E8xxx and an AMD Phenom 8xxx. But less savvy consumers are likely to be misled by what these model numbers actually mean, and shop assistants in retail stores probably won't help much either.

From clocks to model numbers

Once upon a time, processor names were easy to understand. The brand and model name told you the architecture (Pentium, Athlon...) and the number was the frequency of the processor. More gigahertz meant more speed.

Then AMD realised that this wasn't doing it any favours. Clock-for-clock, its processors were punching above their weight. The result was the equivalency numbers like 2500+ which have adorned AMD's consumer processors since the launch of the Athlon XP.

Intel also switched to model numbers in mid 2004. This was the final death knell for marketing processors by their clock frequency. It was also Intel's first admission that the Netburst Pentium 4 wasn't going to fulfil its original goal of 25GHz - particularly as Intel's own Pentium M was also outperforming it clock-for-clock as much as AMD's Athlon 64.

Model behaviour

When Intel and AMD were using very different model numbering systems, this wasn't a problem. After all, a Pentium 4 670 and an Athlon 64 3000+ are obviously incomparable, just as only a fool would confuse a BMW 530 with a Rover 75.

But when faced with a choice between a quad-core AMD Phenom 9500 or an Intel Core 2 Quad Q9450, a PC novice is sure to be scratching their head. They could easily assume the Intel processor is overpriced and the AMD one better value. But we know a 2.66GHz quad-core processor from Intel will run seven rings round a 2.2GHz one from AMD. For many, that's well worth the extra £100.