thumb|An example of an ISA interface card with extremely limited interrupt selection options, a common problem on PC ISA interfaces.Kouwell KW-524J dual serial, dual parallel port, 8-bit ISA, manufactured in 1992:* Serial 1: IRQ 3/4/9* Serial 2: IRQ 3/4/9* Parallel 1: IRQ 5/7* Parallel 2: IRQ 5/7(There is no technical reason why 3,4,5,7,9 cannot all be selectable choices for each port.) Also, although some later ISA devices were capable of automatic configuration, it was common for PC ISA expansion cards to limit themselves to a very small number of choices for interrupt request lines. For example, a network interface might limit itself to only interrupts 3, 7, and 10, while a sound card might limit itself to interrupts 5, 7, and 12. This results in few configuration choices if some of those interrupts are already used by some other device.
thumb|an example of an isa interface card with extremely limited interrupt selection options a common problem on pc isa interfaceskouwell kw-524j dual serial dual parallel port 8-bit isa manufactured in 1992* serial 1 irq 3/4/9* serial 2 irq 3/4/9* parallel 1 irq 5/7* parallel 2 irq 5/7(there is no technical reason why 34579 cannot all be selectable choices for each port) also although some later isa devices were capable of automatic configuration it was common for pc isa expansion cards to limit themselves to a very small number of choices for interrupt request lines for example a network interface might limit itself to only interrupts 3 7 and 10 while a sound card might limit itself to interrupts 5 7 and 12 this results in few configuration choices if some of those interrupts are already used by some other device