Another month, another world-beating CPU from Intel . In April, Intel launched the Core 2 Extreme QX6800. This week, it's taken the wraps off its latest quad-core killer, the monstrous Core 2 Extreme QX6850.

As the minor modification to the moniker indicates, this latest chip is a modest overhaul rather than an all-new CPU. It remains based on Intel's 65nm production process and only ups the ante in terms of headline clockspeed from 2.93GHz to an even 3GHz.

Put another way, that's an enormously underwhelming 2 per cent boost in the headline operating frequency. More noteworthy, however, is the introduction of a significantly faster CPU bus. Previous performance variants of the Core 2 family sported 1,066MHz buses. With the QX6850, Intel has introduced its first 1,333MHz-bus processor for the desktop.

The QX6850: just one of the family

In fact, the QX6850 is just one member of a whole family of new 1,333MHz-equipped processors being launched. A further four models, all more affordable dual-core chips, join the QX6850 at launch. UK retail prices will range from around £100 for the entry level 2.33GHz E6540 to approximately £600 for the flagship QX6850. Taking up the midrange slack are the E6750 and E6850 chips, yours for £140 and £175.

Intriguingly, these prices are actually less than the equivalently-clocked 1,066MHz processors that remain in Intel's price lists for the time being.

If that seems odd, the explanation is simple. Only Intel's latest P35 and X38 motherboard chipsets officially support the new processors. By pricing them below the older, theoretically inferior 1,066MHz CPUs, Intel is clearly trying to encourage system builders to buy into its latest platforms.

All else being equal, therefore, just how much impact does the 30 per cent faster bus have on overall performance? For starters, it's worth noting that it won't make a great deal of difference to the dual-core members of the Core 2 family. Thanks to the snazzy shared cache memory architecture of those chips, bus bandwidth is not hugely critical.

Quad-core conundrum

But it's a different story for Intel's quad-core processors. In fact, Intel's quad-core CPUs to date have been little more than a pair of dual-core processor dies crammed together onto a single CPU package.

And that's important, because it means that any sharing of data or communication between the two dies must travel via the CPU bus. In other words, a journey to the motherboard and back via the Northbridge chip is necessary.