Intel 3.46GHz P4 Extreme Edn and i925XE chipset

Bus master?

TrustedReviews.comReview It wasn't so long ago that Intel released the i925X chipset, and there was a lot to shout about. The chipset broke a lot of new ground, like the introduction of DDR 2 memory, Matrix RAID capability and Hi-Definition Audio. Then there was the long awaited debut of PCI Express. But one thing that remained static: the frontside bus (FSB) speed, at 800MHz, writes Riyad Emeran.

Now, only four months on from the launch of the 925X, Intel is launching the 925XE. How much difference can a single letter tacked onto the end of a chipset name make? Well, to be honest, there isn't a whole host of new features on offer, but there is one definite step forward and that's the FSB speed.

Intel i925XE chipset

With the 925XE Intel is raising the bar again, with the FSB tearing along at 1066MHz. Of course this is utilising a quad-pumped model, so in reality you're getting 4 x 266MHz, as opposed to the 925X chipset which was based on a 4 x 200MHz Quad Pumped model, which achieved the 800MHz FSB.

The main upshot of the increased Front Side Bus is that it stops processor clock multipliers spiralling out of control. Take the Pentium 4 Extreme Edition for instance - this is a 3.4GHz chip, so with an 800MHz FSB you're looking at a clock multiplier of 17x. Using a board with a 1066MHz Front Side Bus allows you to reduce the clock multiplier of a CPU without reducing its frequency. In fact, Intel's new Pentium 4 Extreme Edition runs at 3.46GHz, but only employs a clock multiplier of 13x - obtained by dividing 3460MHz by 266MHz.

As well as the increased Front Side Bus the 925XE also gives you a little boost in the memory stakes. Although the 925X chipset supported 533MHz DDR 2 memory, it was limited to CL4 latency. In fact, we tried dropping the latency down to CL3 on a 925X chipset, and although it seemed to be working fine, when we checked the memory timings after boot-up, they had relaxed to CL4. However, with the 925XE chipset, there is native support for DDR 2 running at 533MHz with CL3 latency - this was borne out when we checked the memory timings on our test rig and were pleased to note that it was running at CL3.

Of course, the 925XE chipset requires a new generation of processors to take advantage of the new FSB frequency, and at present that range consists of just the 3.46GHz P4 EE. This makes a certain degree of sense, since the 925XE platform is definitely geared towards high performance, and the Extreme Edition is Intel's weapon of choice in this arena. As well as the support for the faster FSB, the Extreme Edition also sports a hefty 2MB of L3 cache, on top of the 512KB of L2 cache that's intrinsic to the 130nm P4 breed.

But it shouldn't be too long before we start to see all P4s migrate to the new FSB standard. The current top of the range P4 runs at 3.6GHz, under an 800MHz FSB - this results in an 18x clock multiplier. With that in mind, it's unlikely that Intel will want to push the P4 much further with an 800MHz FSB, since topping 4GHz will mean a clock multiplier of 20x.

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