SCSI cards that run at 80 or 160 megabytes per second can take up so much PCI bandwidth that they deprive your 324 or 424 of enough bandwidth to do their job. It's therefore advisable to set the thruput of such cards to no more than 40 megs per second which is plenty fast for even large high res audio projects. Contact the maker of your SCSI card for details on how to make such adjustments.