The Difference Between The Old And The New IEEE-1180 IDCT
You remember Intel's email from above. Amongst other things, Intel simply re-compiled the original source code of FlasK's IEEE-1180 iDCT that is using the normal x87-FPU. The benchmarks in the Pentium 4 update article were run with this option and you remember that Pentium 4 showed very bad performance. Since the underlying code is the same, the resulting MPEG4-file encoded with the old as well as the new version using the x87-iDCT should obviously be identical (which it is). Let's see what difference the re-compilation of this code actually makes.
I regard it as rather mind-blowing that Pentium 4 as well as Pentium III and Athlon benefited from the re-compilation immensely. It shows that the original compilation of FlasK was either done with an ancient compiler or with very strange optimizations. Intel's version doesn't only improve performance for Pentium 4 owners, but for Pentium III and Athlon owners as well.