Use this utility is to reduce the number of clks that AGP video cards are taking. According to the PCI Latency Timer Howto, 248 clks (a typical value for AGP vid-cards) is about 4 times too much time for any device to grab the bus.

I've noticed that by reducing my GeForce 2/GTS AGP card's PCI latency from 248 clks to 64 clks, I have less problems w/drive-write errors under Windows 98 on my Gigabyte 7ZX when accessing the CDROM and an IDE drive simultaneously (i.e.when loading certain games).

Reducing this timer value (to about 72 clks) didn't affect the performance of my Geforce 2/GTS either. You want to lower the AGP card's PCI latency timer as much as possible and see at what point (if any), it affects your video performance.