This version of the PCI Latency Tool is compatible with Windows XP x64. You must be logged in as an administrator for the tool to install. Most devices support latency values which are multiples of 8 (which means any other value will be rounded).
AGP video cards DO have PCI Latency timers. PCI Express cards DO NOT have PCI Latency timers.
This tweak is an important one, and one well worth checking into. Apparently, newer high-end video cards hog PCI latency for no known reason. This makes other components wait for access and causes stutters and thus lower frame rates. If you adjust the latency this might benefit you, users are reporting big improvements.