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3 Troubleshooting Your PC
Technical Information Needed for Troubleshooting
IRQs, DMAs, and I/O Addresses Used by Your PC
IRQs used by PC
The IRQ, DMA, and I/O address
mappings shown here are for a
PC with a basic configuration.
The resources used by your PC
may vary, depending upon
which accessory boards are
bundled with the PC.
IRQ0 system timer
IRQ1 keyboard
IRQ2 system cascade
IRQ3 free if not used for serial port 2
IRQ4 free if not used for serial port 1
IRQ5 free if not used for parallel port 2
IRQ6 flexible disk drive controller
IRQ7 free if not used for parallel port 1
IRQ8 real-time clock
IRQ9 available for PCI devices, if not used by ISA board
IRQ10 available for PCI devices, if not used by ISA board
IRQ11 available for PCI devices, if not used by ISA board
IRQ12 mouse
IRQ13 co-processor
IRQ14 integrated IDE hard disk drive controller
IRQ15 free if not used by second IDE controller
DMAs used by PC DMA 0 free
DMA 1 free if not used for parallel port in Setup
DMA 2 flexible disk drive controller
DMA 3 free if not used for parallel port in Setup
DMA 4 used to cascade DMA channels 0-3
DMA 5 free
DMA 6 free
DMA 7 free
I/O Addresses used by PC 2Eh - 2Fh, integrated I/O controller
96h - 97h, “Little Ben”
E0h - E7h, HP reserved
170h - 177h, 376h IDE secondary channel
1F0h - 1F7h, 3F6h IDE primary channel
278h - 27Fh parallel port 2
2E8h - 2EFh serial port 4
2F8h - 2FFh serial port 2
378h - 37Fh parallel port 1
3B0h - 3DFh integrated video graphics controller
3E8h - 3EFh serial port 3
3F0h - 3F5h, 3F7h integrated flexible disk controller
3F8h - 3FFh serial port 1
496h - 497h HP reserved
678h - 67Dh parallel port if ECP mode is selected
778h - 77Dh parallel port if ECP mode is selected