[Thinkpad] Tweaking IRQ assignments for PCI Graphics Card in SelectaDock III

I've got a PCI Graphics Card installed in a SelectaDock III with a ThinkPad
770E attached and I am trying to figure out how to assign a unique IRQ to
the graphics card in Windows 98SE. I'll give some quick background and then
return to my problem.

BACKGROUND

At the moment, I have a Pine nVidia TNT2 M64 32MB video card sharing an IRQ
with a XIRCOM CardBus Ethernet/Modem combo card, which is in one of the
PCMCIA slots in the Dock, and with the TI PCI-1250 CardBus Controller which
seems to go along with the CardBus card wherever it goes. (And also with
"PCI Device Setup", which I understand is PCI Steering, so that's okay).
I've got PCI Steering enabled through the ThinkPad Configuration program,
and I've assigned several additional IRQs to PCI Steering. Additional PCI
Steering IRQs are being used by: Creative SB Live 5.1 PCI card in Dock, 2
Intel 82371/AB/EB PCI to USB Universal Serial Bus Controllers, and an
Adaptec AHA-2940AU PCI SCSI Controller. These additional ones are all
internal to the Dock except for the sound card. So in addition to internal
controllers, I've got a video card and a sound card in two PCI slots, and
I've got a modem/ethernet combo CardBus card which also uses the PCI
Steering system for some reason.

Believe it or not, almost everything is now working smoothly with this setup
except that once in a while I get total system freezes (i.e. screen freezes,
mouse and keyboard stop responding, no response to CTRL+ALT+DEL, and the
only solution is to use the physical on/off switch). The freezes occur in a
variety of contexts: playing certain 3D games, browsing the web, or simply
using a file manager. Sometimes I can go for a week without a freeze,
including playing a 3D game for several hours. Other times, it will freeze
more than once in a day.

I have a USB Scanner which I attach when I need it, and I've noticed that I
almost always end up with once of these freezes when the scanner is
attached. So naturally I avoid keeping the scanner attached, but the
freezes also occur without it. I have had suspicions about USB problems
because of the scanner symptom, but the only other USB device I've got
regularly attached is an IBM Media Access Pro Keyboard. I've tried multiple
driver versions for this device to see if that makes any difference. But
even with all the "media access" functions disabled for a 3D game, I will
still sometimes get a freeze. At one point I even reverted to a regular
PS/2 standard keyboard and still got a freeze with that. Other possible
causes of the freezing might be overheating or memory module problems I
guess -- I've replaced the original PII 266MMX chip in my machine with an
Intel PII 400MHz, and I've got two different kinds of 128MB modules
installed -- but the freezing never occurs when I'm undocked and using the
original built-in 4MB video card.

All that is to say that I don't know what is causing the freezes so now I
want to try assigning the graphics card a separate, devoted IRQ and see if
that will help -- and in fact, I'd like to do the same with the sound card
too. Lots of folk with regular desktops seem to agree that doing this can
remove some causes of random freezing.

PROBLEM

The problem is, I don't know how to assign a unique IRQ to my video card.
I've tried playing around with the PCI Steering options in the ThinkPad
Configuration, and I've added additional IRQs for PCI Steering. I don't
seem to be able to control which IRQs get assigned to which cards or which
ones are sharing. Presumably this is by design, and that's the whole point
of having an IRQ sharing system for PCI cards in the first place. But isn't
there a way of "forcing" certain configurations?

I can get the cards to move around to different IRQs simply by changing the
IRQs which I have assigned to PCI Steering -- even just changing the order
of the IRQs I assign to PCI Steering will reshuffle the assignments when I
reboot. But no matter what I do, the CardBus Controller and the dang Xircom
modem/ethernet combo moves to the same IRQ that the video card is on. I can
even free up an additional IRQ and add it to the list of PCI Steering IRQs,
but the system will simply assign one of the other shared devices to it, or
even leave it empty, without assigning anything to it, despite the fact that
the video card is sharing with the modem/ethernet combo card.

Does anyone have any suggestions? Is it even likely that I can solve my
freezing problems by doing this?

Philip Kiff
Canada

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Received on Thu Jul 3 11:47:15 2003