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PCI IRQ and DMA Settings / IRQ <n> Assigned To / DMA <n> Assigned To
When automatic resource allocation is not used, the BIOS allows you to specifically designate which system interrupts (IRQs) and direct memory access channels (DMAs) you want it to be able to use for setting up Plug and Play devices. For each IRQ or DMA, except ones reserved by the system, you can designate either "PCI/PnP" or "ISA/Legacy". When a resource is assigned to "ISA/Legacy" it is declared "off limits" to the BIOS.
The IRQs that you can normally set here are IRQs 3, 4, 5, 7, 9, 10, 11, 12, 14 and 15. The DMA channels are 0, 1, 3, 5, 6 and 7. (The others are reserved by system devices.) The default on most systems for each of these settings is "PCI/PnP". If your system does not have automatic resource allocation (which is preferred) then it is usually best to leave these settings on "PCI/PnP" unless you are having a problem with Plug and Play. For example, if PnP keeps taking a resource for a PnP card that you need for an ISA card, you might want to set that resource to "ISA/Legacy" here to reserve it.
Note: If automatic
resource allocation is enabled, these options will normally either be locked to prevent
change, or even cleared from the screen altogether, since the BIOS will control them