IRQ | DEVICE USED in AT, 386, 486, and Pentium Computers |
0 | System Timer |
1 | Keyboard Controller |
2 | Tied to IRQs 8-15 |
3 | COM 2 |
4 | COM 1 |
5 | LPT2 or Sound Card |
6 | Floppy Diskette Controller |
7 | LPT 1 |
8 | Real Time Clock |
9 | Substitutes for IRQ 2 |
10 | Not Assigned |
11 | Not Assigned |
12 | PS/2 Mouse Port |
13 | NPU (Numerical Processing Unit) |
14 | Primary Hard Disk Controller |
15 | Secondary Hard Disk Controller |
IRQ |
Devices used and potential conflicts |
0 | This IRQ is used within the system board for system timing. If a conflict arises with this IRQ chances are the system board is bad, use a diagnostic program to determine if this is the case. |
1 | This IRQ is assigned to the keyboard. Its never available to other add-in cards. Again if this is the problem, its most likely a problem with the system board. |
2 | This IRQ was assigned to older EGA video cards. Beware, IRQ 9 uses IRQ to communicate with the CPU, therefore this IRQ should only be used under extreme circumstances. |
3 | This IRQ is assigned to the serial ports: COM 2, and COM 4. Avoid setting other devices to this IRQ since mice, modems, and other devices are set to use this IRQ. |
4 | This IRQ is assigned to the serial ports: COM 1, and COM 3. Remember IRQ lines for the most part cannot be shared, so generally you can't have devices on COM 1 and COM 3 that are both active and working. |
5 | This IRQ is assigned to a secondary printer port LPT2, but in the absence of a second printer port, it is used primarily for sound cards, or as an alternative IRQ for the COM ports. |
6 | This IRQ is assigned to the diskette controller. Few if any devices leave this IRQ as an option, since most systems have a floppy drive built into them. |
7 | This IRQ is assigned to the first parallel port LPT1, its also made available to other add-in cards, but should not be used for anything except the printer port to avoid conflicts. |
8 | This IRQ is reserved for the internal real-time clock. This line is never available to other add-in cards. If there is a conflict here, its an indication of a motherboard problem. |
9 | This IRQ uses IRQ 2 to talk to the CPU, so it has a high priority. Its generally used for network cards. |
10 | This IRQ is left open for network cards, sound cards, SCSI host adapters. |
11 | This IRQ is a common one for SCSI host adapters, but can also be used for a variety of other devices. |
12 | This IRQ is used for the PS/2 style mouse port included on many motherboards. If the PS/2 mouse port is enabled in the system's setup program, and you're using a PS/2 connection mouse, don't use this port for anything else, otherwise its an available one. |
13 | This IRQ is reserved for the Numeric Processing Unit (math coprocessor) It is never available for anything else. |
14 | This IRQ is assigned to the primary hard drive interface |
15 | This IRQ is assigned to the secondary hard drive interface. |
DMA Channel |
Devices commonly assigned |
0 | Assigned internal to the system board, you shouldn't be able to use it. |
1 | No specific assignment, although its usually used for sound cards, or SCSI host adapters. |
2 | Assigned to the diskette drives. |
3 | No specific assignment, although its again a common choice for sound cards, network interface cards, or SCSI host adapters. |
4 | No specific assignment |
5 | No specific assignment, however Sound Blaster-type cards generally use this DMA channel |
6 | No specific assignment |
7 | No specific assignment |
I/O Address | Common Device using Address |
130h | Used for SCSI host adapters |
140h | Used for SCSI host adapters |
170h | Secondary IDE Interface |
1F0h | Primary IDE Interface |
220h | Typically used for Sound Blaster-type sound cards |
240h | An alternate address for sound cards |
278h | Assigned to LPT2 or LPT3 and generally used with IRQ 5 |
280h | Network Interface cards or the Aria Synthesizer |
2A0h | An alternate address for NIC cards or the Aria Synthesizer |
2E8h | Assigned to COM 4 and used with IRQ 3 |
2F8h | Assigned to COM 2 and used with IRQ 3 |
300h | Another Network Interface Card choice |
320h | A good place for a Network card, unless there is a SCSI host adapter or MIDI device |
330h | A common place for the SCSI host adapters |
340h | Another good alternative for the SCSI host adapter |
360h | A Network card choice, but beware of the first parallel printer port, this could be a conflict. |
378h | The first parallel printer port (LPT 1) in color systems, commonly used with IRQ 7. |
3BCh | The first parallel printer port (LPT1) in monochrome systems, beware you may have problem assigning this address to a printer port in Windows 95. |
3E8h | Assigned to COM 3 and used with IRQ 4 |
3F8h | Assigned to COM 1 and used with IRQ 4 |
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