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Generally, each driver on your system, including those for network adapters and SLIP lines, must have its own interrupt vector (or ``IRQ''). An interrupt halts processing momentarily so that input/output or other operations can occur. Processing resumes after the specific operation takes place. Consequently, it is important that each device installed in your system be provided with an interrupt setting that does not conflict with the settings used by the hardware and other peripherals (unless the device in question supports sharing of interrupts).
Unless a device supports sharing of interrupts, its interrupt vector must not be used by any other device on the system. Refer to your networking hardware documentation to determine which vectors the hardware supports. The DCU (Device Configuration Utility) lists the hardware already installed on your system and what vectors are already in use.
Standard hardware interrupt vectors (IRQs)
| IRQ | Description (driver) | Notes |
|---|---|---|
| 0 | ~ | Reserved |
| 1 | Keyboard driver (kd) | Reserved |
| 2 | ~ | Available (IRQ 2 is internally mapped to IRQ 9. When choosing IRQ values, you should consider IRQ 2 and IRQ 9 to be the same interrupt.) |
| 3 | Serial COM2 port (asyc) | Reserved if present (unless disabled in the BIOS or with the DCU) |
| 4 | Serial COM1 port (asyc) | Reserved if present (unless disabled in the BIOS or with the DCU) |
| 5 | Cartridge tape (ictha) or parallel port #2 (lp) | Recommended cartridge tape setting if installing from non-SCSI cartridge tape drive and a printer is not assigned to this IRQ |
| 6 | Floppy disk (fd) | Reserved |
| 7 | Parallel port #1 (lp) | Required if present and used at that setting (unless disabled in the BIOS or with the DCU) |
| 8 | Real-time clock (rtc) | Reserved |
| 9 | ~ | Available |
| 10 | ~ | Available |
| 11 | ~ | Available |
| 12 | PS/2 mouse | Reserved if PS/2 mouse us installed |
| 13 | Math coprocessor and programmable interrupt controller (atup) | Reserved |
| 14 | Integral hard disk (dcd/athd) | Only required if an IDE, ESDI, or ST506 hard disk is installed |
| 15 | ~ | Available |
After you determine your hardware's IRQ settings, choose settings for each networking adapter that you plan to install, making sure that the settings do not conflict with each other. The documentation for each networking adapter should indicate whether you need to configure the adapter physically to use the chosen IRQ setting. The operating system reserves interrupt vectors 4 and 7 for COM1 and lpt0, respectively. If you choose any setting that is either a setting reserved for another use or is in use by another device, a conflict occurs. Some SCOadmin managers may be able to detect conflicts.
If yours is an ISA system, your networking hardware might be preconfigured to use a particular vector. If you want to change this vector setting, you might also need to change the physical jumper settings on the adapter or run a setup program provided with the adapter.