Mark Derbyshire writes: "We do a lot of ultra wide SCSI with our Macs using both ATTO ExpressPCI (dual channel) and Adaptec PowerDomain 3940W (dual channel) PCI cards. Generally the ATTO cards are faster. We recently put an ATTO card into our Apple 233 MHz G3 desktop and the boot process hung even before the happy Mac shows up (the mouse cursor freezes on the blank gray screen)." He contacted ATTO about this and they replied: "The dual channel is not compatible with the G3 platform. Apple is currently working on a fix for this. In addition, two PSC SC cards will not work in the slots because this acts like a dual channel."