Re: Question: Multiple Super Serial Card ][s in //e?

[david@uow.edu.au (David Wilson)]

"Mark Cummings" <NOTfigjams@primus.com.au> writes:
>Actually the Apple has two interupts, IRQ and NMI. The IRQ being software
>maskable during un-interuptable operations such as disk access, provided the
>software is written correctly.

>On the PC side, IRQ sharing is not so friendly.

But it is getting better. The problem was with the original ISA bus. It uses
edge triggered active high going IRQ lines. These cannot be shared by two
or more cards. The PCI bus uses level sensitive active low lines just like
the IRQ line on the Apple II and provided the drivers are correctly written
any number of cards can share the same IRQ line.
--
David Wilson  School of IT & CS, Uni of Wollongong, Australia