Standard DMA, I/O and IRQ Assignments
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| DMA | Function | Bus slot required |
|---|
| 0 | Unused | Yes (16-bit) |
| 1 | Unused | Yes (8-bit) |
| 2 | Floppy disk controller board | Yes (8-bit) |
| 3 | Unused | Yes (8-bit) |
| 4 | First DMA controller IC | No (motherboard) |
| 5 | Unused | Yes (16-bit) |
| 6 | Unused | Yes (16-bit) |
| 7 | Unused | Yes (16-bit) |
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| Address | Assignment |
|---|
| 000h-00Fh | 8237A-5 DMA Controller IC #1 |
| 020h-03Fh | 8269A Programmable Interrupt Controller IC #1 |
| 040h-05Fh | 8254-2 System Timer IC |
| 060h | 8042 Keyboard/Mouse Controller IC |
| 061h | System board I/0 port |
| 064h | 8042 Keyboard/Mouse Controller IC |
| 070h-07Fh | RTC port and NMI mask port |
| 080h | POST code port |
| 080h-09Fh | 74LS612 DMA Page Registers |
| 0A0h-0BFh | 8237A-5 Programmable Interrupt Controller IC #2 |
| 0F0h | Clear math coprocessor busy |
| 0F1h | Reset math coprocessor |
| 0F8h-0FFh | Math coprocessor ports |
| 1F0h-1F8h | Hard disk controller ports (Primary IDE) |
| 170h-178h | Hard disk controller ports (Secondary IDE) |
| 200h-20Fh | Game control ports |
| 238h-23Bh | Bus mouse adapter ports |
| 23Ch-23Fh | Alternative bus mouse adapter ports |
| 278h-27Fh | Parallel printer 2 (LPT2) |
| 2B0h-2DFh | Alternative EGA ports |
| 2E0h-2E7h | GPIB (Adapter 0) |
| 2E8h-2EFh | Serial port 4 (COM4) |
| 2F8h-2FFh | Serial port 2 (COM2) |
| 300h-31Fh | Unassigned |
| 360h-363h | Network card ports (low) |
| 368h-36Bh | Network card ports (high) |
| 378h-37Fh | Parallel printer 1 (LPT1) |
| 380h-38Fh | SDLC (bisyne 2) ports |
| 3A0h-3AFh | Bisyne 1 ports |
| 3B0h-3BBh | Monochrome display adapter (MDA) ports |
| 3BCh-3BFh | Parallel printer 3 (LPT3) |
| 3C0h-3CFh | Enhanced graphics adapter (EGA) ports |
| 3D0h-3DFh | Color graphics adapter (CGA) ports |
| 3E8h-3EFh | Serial port 3 (COM3) |
| 3F0h-3F7h | Floppy disk controller ports |
| 3F8h-3FFh | Serial port 1 (COM1) |
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|
| IRQ | Function | Bus slot required |
|---|
| 0 | System timer IC | No (motherboard) |
| 1 | Keyboard controller IC | No (motherboard) |
| 2 | Second IRQ controller IC | No (motherboard) |
| 3 | Serial port 2 (COM2) | *Yes (8-bit) |
| 4 | Serial port 1 (COM1) | *Yes (8-bit) |
| 5 | Parallel port 2 (LPT2) | *Yes (8-bit) |
| 6 | Floppy disk controller board | *Yes (8-bit) |
| 7 | Parallel port 1 (LPT1) | *Yes (8-bit) |
| 8 | Real-time clock (RTC) | No (motherboard) |
| 9 | Unused (redirected to IRQ 2) | Yes (8-bit) |
| 10 | Unused | Yes (16-bit) |
| 11 | Unused | Yes (16-bit) |
| 12 | Motherboard mouse port (PS2) | *Yes (16-bit) |
| 13 | Math coprocessor | No (motherboard) |
| 14 | Primary IDE Hard disk controller board | *Yes (16-bit) |
| 15 | Secondary IDE Hard disk controller board | *Yes (16-bit) |
* Please note that most of these devices are now integrated into the motherboard and no longer require slots.
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Basic Troubleshooting Steps
