[Open-graphics] Video interrupt enable/disable

[Timothy Normand Miller]

On 4/17/07, James Richard Tyrer <tyrerj at acm.org> wrote:

> Have I been the victim of Intel hype?  They make hardware that would
> make it possible to have enough interrupts for each PCI card slot to
> have 4 interrupts or at least to have 24 hardware interrupts available
> to be assigned with a cross point.

On a PCI bus, there are four interrupt lines.  All four are connected
to each slot, but in a different order.

In some Sun hardware, each slot has its own set of interrupt lines.
But they do other weird stuff too.

Also, in general, there are many sources of interrupts in a PC, but
they all route to one priority encoder that hands a binary number to
the CPU that tells it which one to pay attention to.  Then it comes
down to the ISR looking to figure out which source it is and so forth.

You're never going to get away from the fact that you have to query
devices to figure out which one asserted the interrupt, because you
cannot tell just from the interrupt number.

-- 
Timothy Normand Miller
http://www.cse.ohio-state.edu/~millerti
Open Graphics Project