I've tried 2 different PCI express cards in a 2010 Mac Pro and have the following observations: Boot time increases substantially... my guess it's taking longer to identify boot disks. Disk performance via PCI express is worse than just plugging straight into a SATA slot: even with using a 6G PCIe eSata card to a RAID 0 enclosure. Moving a PCI card from the mac to a pc & performance on the pc is much higher than that on the mac/SATA slot. This is an expensive trial & error approach & I really don't want to spend more $'s on boards that exhibit the same problems. Is there a decent PCI express board that will allow for improved disk (ssd) I/O performance or is there a known issue?