Thank you JMS for your very informative reply.
Further comments/questions below. Se also my reply to Bug Hunter
(funny name :).
Thanks,
Svante
[EMAIL PROTECTED] writes:
>
> Initially the BIOS handles setting up the IRQ's for your cards as
> the system comes up.
> The OS can modify this allocation as needed, within certain limits.
> The problem is that you are running up against one of the most
> often mis-understood limits.
>
> Here goes:
> Yes, as people here will indicate, you can CHANGE the IRQ utilized
> for a card, -BUT- in so doing you will not change the assignment of
> that one card. You will change the assignment of MULTIPLE devices
> or slots!
>
> Huh?
> PCI was initially designed to handle only three devices. As a
> result as manufacturers started adding PCI slots, they took to
> wiring two or more PCI slots together. Thus your AGP slot almost
> always shares an IRQ with the first PCI slot.
>
> Why?
> Well in their infinite wisdom, they deemed that if you were using
> an AGP video card, you would NOT also be using a video card in slot
> one and vice versa.
>
> Ugh, so you normally can use one or the other, but not both without
> resorting to some trickery called IRQ Steering.
>
> On newer motherboards two or more PCI slots may share an IRQ
> allocation with integrated devices. Thus, in your case the PCI slot
> you put the ethernet card into WILL ALWAYS share the same IRQ with
> your motherboard's integrated audio. NO MATTER WHAT YOU DO, this
> will be the case. You can change the allocation to say 11, but now
> your audio and eth0 will go to 11... ugh.
This would be OK if the video card does not require an IRQ, or can
more than two devices share the same IRQ? (W98 on the same machine
have no problems with three devices at IRQ5)
I'm using X4.0.2 with DRI enabled. According to the log files and
glxinfo the card is HW accelerated. However, even though Q3A and gears
run OK, HG2, Heretic2, UT does _not_. Do the Banshee (tdfx) driver
require an IRQ? If not everything should be OK, or something else is
causing the complete slowdown, maybe DMA?
>
> Your only choice is to move the ethernet card to another slot to
> avoid sharing IRQ's..... ISA PNP cards don't suffer from this. In a
> way they are more flexible with resource allocation.
What happens if I exchange the Ethernet card (IRQ 5) with the PCTV
card (IRQ 3)? Then according to your info IRQ 5 will be allocated to
the sound device, the TV card and the Banshee (AGP) card and IRQ 3 to
the Ethernet card. If all devices requires an IRQ, no solution is
obtained this way!?
>
> If you are using an ISA PNP card you might be able to change the
> IRQ it uses with software provided by the manufacturer... This
> software modifies the "hint" that the card reports to the bios
> during boot. The preferred IRQ is stored on the card itself, and
> the bios sets up the card to use the IRQ "hinted" at by the on
> board NVRAM (or in some cases other forms of non-volatile RAM).
No ISA slots are avilable on this computer :(
>
> Since you've already stated that you have limited slots available,
> your only recourse is to either move things around, remove a
> device/card, get a new non-conflicting device or card, or a new
> computer.
>
> Welcome to the world of IBM based design architecture.
>
> Needless to say this all needs a MAJOR overhaul, but who is going
> to set the standards?
>
> -JMS
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of Svante Signell
> Sent: Friday, December 29, 2000 11:15 AM
> To: [EMAIL PROTECTED]
> Subject: [expert] IRQ steering?
> Anyone knows how IRQ 5 is chosen both for my eth0 (tulip, external
> card) driver and sound (maestro, on motherboard) on my Compaq Presario
> 5640/5670 when other interrupts are available: 4,6,7,9,10,11?
...
