[OT] IRQs above 15 in Linux

Aaron Howell aaron at kitten.net.au
Thu Sep 19 18:47:39 EDT 2002


Actually Linux does use irqs higher than 15.
i've only ever seen it on smp boxes though.
Perhaps it also happens on uniprocessor ones if Linux has to do irq sharing between pci devices.
Regards
Aaron
On Thu, Sep 19, 2002 at 05:40:11PM -0500, Gregory Nowak wrote:
> I don't understand. If I am correct, then there are only irqs from 1 to 15, and they are dependent on the hardware, not on the os. So, it isn't possible that the linux kernel is using irqs higher then 15. 
> Greg
> 
> 
> On Thu, Sep 19, 2002 at 05:26:12PM -0500, Adam Myrow wrote:
> > I know this is off topic a little, but I can't find anything on it.  As I
> > reported previously, when I installed my Linksys NIC, Windows 95 disabled
> > my sound card and said it has a resource conflict.  Linux has had no
> > trouble with it.  Now, I know why.  Windows uses IRQs from 1 to 15, while
> > Linux uses IRQs above 15.  For example, my modem is on IRQ 17 and my NIC
> > is on IRQ 19.  It only seems to do this with PCI devices, so I assume it's
> > a PCI-specific feature.  What I'm trying to find out is if any version of
> > Windows can be made to use high IRQs like that, or where the feature is
> > explained on a more technical level.  I've done searches on various search
> > engines, but can't seem to find anything.  If anybody has a clue on this,
> > let me know.  Thanks.
> > 
> > 
> > 
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