Originally Posted by siddly
I disabled IOMMU in the BIOS and it booted without USB and ethernet and it didn't get to a desktop.
I powered down, drained the BIOS for around 10 minutes. Booted with default settings which came up with IOMMU disabled - failed to boot.
Had to play with BIOS settings including enabling IOMMU to get it to boot back to the old state where X only starts with the vesa driver.
Don't drain the BIOS to reset it, just get into it and there is an option to reset to factory "optimized" defaults. That is all that should be needed (assuming you are running the 0901 BIOS). I have the exact same board with a GTX-580 and the exact same issue (which is also present in a M5A97 EVO with a GT 520 as well).