[OT] IRQs above 15 in Linux

[OT] IRQs above 15 in Linux

[Adam Myrow]

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.

Re: [OT] IRQs above 15 in Linux

[Gregory Nowak]

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.
> 
> 
> 
> _______________________________________________
> Speakup mailing list
> Speakup@braille.uwo.ca
> http://speech.braille.uwo.ca/mailman/listinfo/speakup

Re: [OT] IRQs above 15 in Linux

[Gregory Nowak]

Sorry, I meant to say irqs 0-15.
Greg

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.
> > 
> > 
> > 
> > _______________________________________________
> > Speakup mailing list
> > Speakup@braille.uwo.ca
> > http://speech.braille.uwo.ca/mailman/listinfo/speakup
> 
> _______________________________________________
> Speakup mailing list
> Speakup@braille.uwo.ca
> http://speech.braille.uwo.ca/mailman/listinfo/speakup

Re: [OT] IRQs above 15 in Linux

[Aaron Howell]

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.
> > 
> > 
> > 
> > _______________________________________________
> > Speakup mailing list
> > Speakup@braille.uwo.ca
> > http://speech.braille.uwo.ca/mailman/listinfo/speakup
> 
> _______________________________________________
> Speakup mailing list
> Speakup@braille.uwo.ca
> http://speech.braille.uwo.ca/mailman/listinfo/speakup

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Re: [OT] IRQs above 15 in Linux

[Adam Myrow]

At 08:47 AM 9/20/02 +1000, you wrote:
>Actually Linux does use irqs higher than 15.
>i've only ever seen it on smp boxes though.

That's funny you should mention SMP boxes.  This machine of mine is an 
SMP-capable machine, but it only has one CPU.  I sort of wonder if extra 
IRQ numbers are a part of the SMP spec?  Whatever the case, it effectively 
lets me have more cards under Linux than is possible under Windows.  I've 
got 4 PCI cards and 2 ISA cards.  They consist of a Dectalk PC which gets 
used under Windows, a Soundblaster AWE64, an Adaptec PCI SCSI card for my 
scanner, a Smartlink Modem that uses the Topic chipset making it usable in 
Linux, and my Linksys ethernet card.  I saw some settings in Windows to use 
PCI 2.1 extensions and stuff about IRQ steering, and will look into this, 
but I sort of doubt I'll come up with much there.  As you can see, my 
system is just full of hardware.  More than likely, I'll eventually get a 
new computer and turn this old one into a strictly Linux box and probably 
the new computer will be dual boot between some version of Windows and Linux.

Re: [OT] IRQs above 15 in Linux

[Kerry Hoath]

Your board has APIC enabled. This
is an Advanced programmable interrupt controller.
They are used on modern boards for smp (multi-processer systems)
and for better PCI resource allocation.
Your linux kernel has APIC support enabled; see the boot up messages.
Windows won't put a soundcard on a high-order irq above 15 becasue
dos boxes can't use the card; dos can't hook the
hardware irq line from the APIC controller since t he dosbox runs
in vm86 mode.
Windows XP supports apic and high-order irqs; not sure
about windows 98 and below. NT4 doesn't.
Either try Windows XP or ME
or disable APIC i n bios.

Regards, Kerry.
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.
> 
> 
> 
> _______________________________________________
> Speakup mailing list
> Speakup@braille.uwo.ca
> http://speech.braille.uwo.ca/mailman/listinfo/speakup
> 

-- 
Kerry Hoath:  kerry@gotss.net kerry@gotss.eu.org or  kerry@gotss.spice.net.au
ICQ: 8226547 msn: kerry@gotss.net Yahoo: kerryhoath@yahoo.com.au