Computer Hardware User Manual

1-12 Chapter 1: Product introduction
IRQ assignments for this motherboard
ABC D
PCI slot 1 used – – –
PCI slot 2 – – – used
PCI slot 3 – – used –
AGP slot – used – –
1.10 Expansion slots
The A7N8X-VM/400 motherboard has three (3) PCI and one (1) Accelerated
Graphics Port (AGP). The following sub-sections describe the slots and the
expansion cards that they support.
1.10.1 Configuring an expansion card
Some expansion cards need an IRQ to operate. Generally, an IRQ must be
exclusively assigned to one function at a time. In a standard design configuration,
16 IRQs are available but most are already in use.
Normally, 6 IRQs are free for expansion cards. Sometimes IRQs are “shared” by
more than one function; in this case, IRQ assignments are swapped automatically
or adjusted through the BIOS firmware.
Standard Interrupt Assignments
IRQ Standard Function
0 System Timer
1 Keyboard Controller
2 Programmable Interrupt Controller
3* USB Universal Host Controller
4* Communications Port (COM1)
5* Onboard Audio
6 Standard Floppy Disk Controller
7* Printer Port (LPT1)
8 System CMOS/Real Time Clock
9* Onboard LAN
10* USB Universal Host Controller
11* Onboard VGA
12* PS/2 Compatible Mouse Port
13 Numeric Data Processor
14* Ultra ATA Controller
15* Secondary Ultra ATA Controller
*These IRQs are usually available for ISA or PCI devices.