I have LHe card on HP workstation 16g ram and have continuous stuttering playback of HD files. SD works fine. I have tested the same files on an old Mac Pro 1.1 with same card and only 4g ram and it plays fine.
Both computers have internal raids that generate 188mps, and the Mac even plays fine on another drive that only reads at 65. I've tried all the settings I can think of, but am obviously missing something.
PC has Nvidia GTX 480 for Mercury playback and Premiere Pro 5.0.3 with correct drivers for that version.