Asus crosses Intel with PAT compatibility claim

Is its mobo's chipset an i865 or an i875?

Asus is on course to clash with Intel over whether its Springdale-based mobo, the P4P800 offers features provided by Intel's Canterwood chipset.

Launched in April, Canterwood, aka the i875, offers what Intel calls Performance Enhancement Technology (PAT). Essentially, that means the chipset uses more aggressive memory timings to achieve a 3-5 per cent performance boost.

Intel launched Springdale, the i865, t'other week as a lower-end alternative to Canterwood. Both chipsets support the Pentium 4 operating over a 200MHz frontside bus quad-pumped to an effective 800MHz.

Yesterday, Asus announced its 865-based P4P800 Deluxe mobo shipped with the ability to turn on PAT via the company's own BIOS, a note spotted by ExtremeTech's Mark Hachman. In short, with one easy tweak your 865 has become an 875 - ironic, given PAT is one of the few things that differentiates the 875 from the 865.

Today, Intel dismissed Asus' claim. A spokesman said that PAT is "hardwired" into the 875 - it can't be enabled in the 865. "PAT cannot be enabled on a 865-based motherboard," he told ExtremeTech.

So who's right? One analyst cited by the ExtremeTech believes the two chipsets are fundamentally identical - it's just a matter of those that perform the best with the more aggressive memory timings being labeled 875s, and those that don't being sold as 865 parts.

That's certainly what happens with processors. Manufacturer A fabs a whole batch of processors and tests them at a given clock speed. If they work, they're sold at that frequency. If not, they're tested at a lower frequency, with the speed being dropped until the chip passes the test. Those that fall below a certain threshold are trashed. So a single Pentium 4 wafer can yield a number of 3.06GHz parts, 2.8GHz chips, 2.6GHz chips and so on.

Intel could be using the same trick with the 875 and 865, and Asus is simply overclocking the 865 to the level Intel clocks the 875.

Alternatively, just as the latest Celerons are basically Pentium 4 processors with some features removed or disabled, so the 865 may not be an 875 per se. However, Asus may have figured out how to overclock the timings to gain an 875-class performance increase. It can't be that to find a 3-5 per cent gain.

Either way, what matters is the performance gain, not necessarily how it was achieved. Independent tests will be required to compare the P4P800 Deluxe to an 875-based mobo to verify Asus' performance claims. Of course, any attempt at overclocking risks pushing the component above the threshold at which it's happy operating, leading to malfunctions. That's why Intel doesn't simply ship all its CPUs at the maximum possible clock speed. So tests will be needed to determine the Asus board's operational durability.

Meanwhile, what will Intel's reaction be? Most likely it will demand Asus stop claiming it can offer PAT on an 865-based board. In which case, Asus will presumably just ship the board as supporting its own Memory Acceleration Mode, which is the option users select in the BIOS to enable PAT. ®

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ExtremeTech: Enhanced Asus mobo may draw Intel's ire