When I used with Radeon VE dual head, the RAID BIOS won\'t even load. But used Matrox G450 Dual works fine.
According to PC specifications, BIOS C,D segment size total is 128k for device sharing, in this case , there might be some device which usually the case is VGA using 64k at BIOS C,D segment and Promise ROM is taking 64k too, when USB legacy Support is enabled in the BIOS then to disabled Promise ROM because of not enough resource for share at that time.
In the BIOS setup/advanced chipset feature
Disable USB Keyboard Support
Disable USB Mouse Support
USB Keyboard & Mouse Support refer to USB support in DOS mode & has nothing to do with USB support in Windows Operating System.