This article is from a FAQ concerning SCO operating systems. While some of the information may be applicable to any OS, or any Unix or Linux OS, it may be specific to SCO Xenix, Open There is lots of Linux, Mac OS X and general Unix info elsewhere on this site: Search this site is the best way to find anything.
An "interrupt is private" message means that you have an interrupt conflict on something critical- usually your controller. If this isn't a new install, it's probably because you removed some device and that caused the BIOS to reassign the interupts, creating a conflict. The solution is to go into the BIOS and tell it NOT to use that interrupt for Plug and Play/PCI devices. Hopefully that will get you back to where you were.
Interrupt changes on PCI machines can happen for reasons as simple as accidentally unplugging the mouse. What happens is this: the mouse uses interrupt 12, so when it is present, 12 will not be assigned to any other device. If the mouse gets unplugged and you reboot, 12 is now available and will get assigned, which throws off everything else, and therefore can kill nic cards and disk controllers that the system was expecting to be at a different interrupt.
The "no root controller" message can come from that, but if you are getting that on an INSTALL, it usually means that you need a BTLD (Boot Time Loadable Driver) for your controller.
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