Use of IRQ 2/9

[Uwe Doering]

john at jwt.UUCP (John Temples) writes:

>I tried installing an eight port serial card on IRQ 2.  I told the
>serial driver (FAS) it was on IRQ 9.  It didn't work.  I moved the
>interrupt to IRQ 7, and all was fine.  My question is, does anyone
>know what the "rules" are when using IRQ 2?  Can it be used with
>16-bit boards that are using IRQs >9?  I had a couple of i860
>coprocessor boards in the system at upper IRQs, and I was wondering
>if this was the problem.

Many EGA and VGA cards use IRQ2/9. You have to disable this on the
video card to have this IRQ line available for FAS. If there is no
jumper for this purpose on the video card you need to cut the trace
that leads to the B4 bus contact. This does the same as pulling the
jumper. This video interrupt (vertical retrace) isn't used for anything
these days, neither under DOS nor UNIX.

FAS (even if configured for IRQ2/9) will work together with cards that
use IRQs >9. For instance, I have two Adaptec ESDI disk controllers in
my computer that use one of these IRQs, each.

     Uwe
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