Prescott, the new version of Pentium 4, got a rather chilly reception from the press and enthusiasts when it was released. In many cases it turned out that the 50% longer pipeline had the ability to make the processor slower than it’s Northwood-equivalent.
Accelenation has tested a Northwood 3.2 Ghz against a Prescott 3.2 Ghz in a series of tests with and without HyperThreading.
Also here we find the same relation as we have seen earlier tests considering performance. Often the performance gain of hyperthreading is actually less on Prescott.
Intel has a chance to improve the situation though since the new SSE3 contains, among others, two HyperThreading-related instructions that eventually will raise performance somewhat.
Read more here.