Comment 5 for bug 859137

I am also affected by this problem.

I am just finalizing a migration of my Ubuntu 11.04 to a Phenom II X6 1100T Processor mounted on an Asus Crosshair V Formula, with 8GB RAM. I have also found the hard way that if I enable the IOMMU MODE in the North Bridge Configuration screen, then I cannot even log on to my system because both my keyboard and mouse (USB) just don't work. Setting the "IMMU MODE" to DISABLED allows me to use my usb keyboard and usb wireless mouse.

From the perspective of an user who uses usb keyboard and mouse and has just enabled the IMMU mode, the Ubuntu system will be completely broken, completely irresponsive, where not even the Alt-SysRq R-E-I-S-U-B sequence could help because there is no keyboard.