Pentium 4: Overclocking

How fast will it go?

Intel frowns on overclocking, but has always released engineering sample (ES) chips which are free from muliplier locking, allowing the brave to experiment with trying them at higher than rated speeds.

Our 1.5GHz P4 is an ES part and the BIOS of the Intel Garibaldi mobo allows clock speed to be set at 100MHz increments between 1.2 and 1.8 GHz. Needless to say, we tried it first at 1.8.

Some devious mechanism somewhere immediately set this back to 1.6GHz, suggesting that our sample processor is in fact a 1.6GHz part (production Intel processors automatically set Intel chipsets to run at their official speed).

The system ran without a glitch for over four days (running SETI at Home in its 'run continually' mode showing a processor utilisation of 100 per cent. It ran completely cold.

Sandra benchmarks showed the following differences between 1.5 and 1.6GHz:

P4 1.5GHz: CPU: 2866 MIPS, FPU: 882 MFLOPS
P4 1.6GHz: CPU: 3004 MIPS, FPU: 947 MFLOPS

P4 1.5GHz: ALU/Mem: 1311 MB/s, FPU/Mem: 1340 MB/s
P4 1.6GHz: ALU/Mem: 1339 MB/s, FPU/Mem: 1364 MB/s

It's pretty impressive to find an early version of a processor capable of running effortlessly at a higher than advertised speed and indicates that the 1.7GHz and 2GHz versions are very close indeed, even at the comparatively clunky 0.18 micron process.

This is a CPU design with a lot of headroom. By this time next year, with the die shrink to the 0.13 micron process, 3GHz should be firmly on the horizon, if not closer.

Pentium III and Athlon have reached the point where an increase in clock speed generates heat rather than better performance. They are old technologies almost at the limit of their capabilities at 0.18 micron. A move to a smaller process will enable a few hundred more MHz to be wrung out of them, but they are both banging their heads on an absolute performance ceiling.

The P4 architecture (we can't bring ourselves to call it NetBurst ™ - sounds too much like a fruit drink) on the other hand has a great deal of growth potential. Compare the performance of the first Pentium Pros at 120MHz with today's top of the range 1GHz PIII chip and you'll see what we mean.

Today's P4 at 1.4GHz is the equivalent of the Pentium Pro's P6 architecture running at 120MHz - that should give you an idea of how fast this sucker will be running in a couple of years' time. ®

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