*Try booting with the "Shift" key held down in order to disable the extensions. If the system boots, remove extensions one at a time to find the extension conflict.
* Diable the ATTO Extension using Extensions Manager (control panel) *This extension is not needed and can be left off.
* If the system still hangs with extension off, try refreshing PRAM. PRAM can become corrupted when changing the hardware configuration of a Macintosh. Hold down the "Command-Option-P-R" keys while starting up the system. Continue to hold down the keys until startup chime is heard three or four times.
* Check for a hardware conflict. Unsupported devices on the ATTO host adapters may cause hangs while attempting to load device driver extensions.
* Remove any other PCI cards, restart. If system boots, add PCI cards one at a time to look for conflicts.
* Try putting the ATTO host adapter in a different PCI slot.
* Make sure you are using the latest ATTO firmware.