IF THE information published by two Asian websites in the last week is correct, it indicates that Intel might have to go quite a lot further to maintain its performance claims not now, but in the future too. The articles appear to be based on two separate steppings of Prescott CPUs. The notes on the compterdiy site indicate that the new Pentium 4 core (Prescott), may be running 14 per cent slower than the older core (Northwood), indicating that it could have between six and eight extra pipeline stage. Each stage could gobble up about two per cent of performance.
The hardware juries, when their NDAs expire very soon now, will find it hard to tell exactly what"s happening because of other features in Prescotts that speed up performance. The other comparison – at pconline - appears to be a different, later, stepping and appears to show that in this stepping the Prescott is between two and five per cent faster that the earlier one. Intel may have re-ordered execution sequence to improve the timings.
The interesting thing with this later stepping, if the site indeed has Prescott samples, is that the ALU (arithmetical logic unit) isn"t double clocked anymore, demonstrated by the drop in Dhrystone numbers compare to the Whetsone ones. In the Prescott"s favour is that the increased caches and branch prediction turn the pipeline losses into a 35% performance improvement. If the numbers are to be believed, 20% of that is because the L1 D cache has risen from 8K to 16K.