Interrupt vectors

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 hwconfig(C) and vectorsinuse(ADM) commands list the hardware already installed on your system and what vectors are already in use.

Table A-1 Typical interrupt vectors

 ----------------------------------------------------------------
 Hardware                    Interrupt Vector (IRQ)
 ----------------------------------------------------------------
 ISA, EISA, or MC machine
   clock                               0
   console (keyboard)                  1
   floppy disk controller              6
 Hard disk controller                varies
 Serial ports
   COM1                                4
   COM2                                3
 Parallel ports
   lpt0, lpt1                          7
   lpt2                                5

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.