Avoiding interrupt clashes on PCI/ISA bus machines

On machines with both PCI and ISA buses, the PCI auto-configuration code cannot read the configuration of cards in the ISA bus slots. You must use the computer manufacturer's setup program to tell the auto-configuration code which interrupts are in use by ISA bus cards. If you do not mark these interrupts as ``used'', it is possible that there will be an interrupt clash between an ISA bus card and a PCI bus card.