Page "Interrupt" Paragraph 9

Some devices with a badly designed programming interface provide no way to determine whether they have requested service.

They may lock up or otherwise misbehave if serviced when they do not want it.

Such devices cannot tolerate spurious interrupts, and so also cannot tolerate sharing an interrupt line.

ISA cards, due to often cheap design and construction, are notorious for this problem.

Such devices are becoming much rarer, as hardware logic becomes cheaper and new system architectures mandate shareable interrupts.