Quicktime 7.2 has a playback issue with Athlon XP processors

Question

Using a 640X480 h.264 quicktime video (aac audio) I have tried to do playback on 4 different Windows XP SP2 systems. They each have an Athlon XP 2800+ (2.1Ghz) processor in them. Each system had various sound cards and video cards (nVidia and ATI). They each had around 1 Gigbyte of memory. These systems would stutter badly while trying to playback these videos and uses 100% of the cpu.
The same videos played on a 2.4Ghz P4 system use about 75% of the processor and playback smoothly. On a Athlon 64 2.21 X2 (using only 1 core) the videos playback using an average of about 25% of the cpu.
The AthlonXPs are all barton or Thoroughbred cores, so they have mmx, sse, and 3dnow. All video/audio drivers have been updated to the newest.
I have messed with all of the video acceleration settings and audio settings (wave only) with the same effect.
Is the h.264 codec just not optomized for this cpu? Are these cpus missing some sort of SIMD set that quicktime needs? Like SSE2?

Answer 1

Odd. I've been tracking reports of the performance problems or system crashes involving playing a video, and hadn't noticed a specific spike hitting folks with AMDs/Athlons. (If anything, it's been most closely related to Intel.)
Just doublechecking something. In the course of your checking on the Video settings, had you looked at disabling your Direct3D acceleration?
(Usually, an issue with that manifests as a green screen when playing the videos, or seeing blotches of pretty colors rather than normal video, or "washed out" pale video rather than the sort of performance issues you're getting, though.)
Is there a Conexant AC chip on any of the systems? Sometimes the power management settings on one of those can cause odd playback symptoms in similar ways to what you're describing (although it's kind of rare by comparison with the nVidia SATA controller issues or the Intel Matrix Storage Manager RAID controller issues).