Intel 945GNT PCI and IRQs

[Ultra5]

Does anybody know how to change the IRQ's associated with the different PCI
slots on the Intel 945GNT motherboards?

We have used Intel motherboards in the past (the last ones were 915 chipset
based) with the iRMX OS and some PCI cards (network, Digi CX concentrator
cards and our own custom board) and all of the drivers need their own
interrupts but the motherboard BIOS has always allowed us to assign them so
we can guarantee they aren't shared. I can't find the same options on the
945 motherboard BIOS. There are 4 PCI slots on the board and 3 of them all
share an interrupt.

Obviously, the best thing to do is to make the drivers use shared interrupts
and since we do have source code for two of them, this is most likely where
we will go. But in the meantime I wanted to check and see if anybody knew
how to assign IRQs like previous chipsets. Are there any ways to re-assign
IRQs after the BIOS does it's thing? It's not like there aren't any free
interrupts or anything, the BIOS just decides it wants them all to share.

 

[George Macdonald]

Does anybody know how to change the IRQ's associated with the different PCI
slots on the Intel 945GNT motherboards?

It's been years since I looked at an Intel branded mbrd but they were
always meagre on BIOS controls... though I'd think there must be a
back-door key-combo "switch" which opens up more options.

We have used Intel motherboards in the past (the last ones were 915 chipset
based) with the iRMX OS and some PCI cards (network, Digi CX concentrator
cards and our own custom board) and all of the drivers need their own
interrupts but the motherboard BIOS has always allowed us to assign them so
we can guarantee they aren't shared. I can't find the same options on the
945 motherboard BIOS. There are 4 PCI slots on the board and 3 of them all
share an interrupt.

Obviously, the best thing to do is to make the drivers use shared interrupts
and since we do have source code for two of them, this is most likely where
we will go. But in the meantime I wanted to check and see if anybody knew
how to assign IRQs like previous chipsets. Are there any ways to re-assign
IRQs after the BIOS does it's thing? It's not like there aren't any free
interrupts or anything, the BIOS just decides it wants them all to share.

Have you looked at a mbrd from a reputable source like Asus or MSI - they
have always tended to allow much more control in BIOS Setup. I must say I
haven't checked but it's been my impression, with those boards, that if you
turn off ACPI support in BIOS Setup and set the PnP OS switch to disabled
you should get IRQs assigned individually to devices. Even recent ones
still allow for the explicit assignment of resources (IRQ, I/O addr, DMA)
to specific slots.

 

[Tony Hill]

Does anybody know how to change the IRQ's associated with the different PCI
slots on the Intel 945GNT motherboards?

It would be largely dependant on several features. The BIOS and the
OS both have a big hand in this and whether they are using APIC or the
legacy method of doing things will affect things a lot.

We have used Intel motherboards in the past (the last ones were 915 chipset
based) with the iRMX OS and some PCI cards (network, Digi CX concentrator
cards and our own custom board) and all of the drivers need their own
interrupts

Those are some *very* poorly written drivers!

but the motherboard BIOS has always allowed us to assign them so
we can guarantee they aren't shared. I can't find the same options on the
945 motherboard BIOS. There are 4 PCI slots on the board and 3 of them all
share an interrupt.

Is your OS APIC aware? if so than it is the OS and not the BIOS that
will have the final say in how the interrupts are allocated.

Hmm.. it looks like this 'iRMX' thing is a Real Time OS for Windows?!?
Ugg! No wonder the thing has so many problems! :>

FWIW though I did a quick search and it looks like iRMX does indeed
support APIC (at least in current versions). So first you'll need to
make sure that you're using APIC mode (this requires enabling it in
the BIOS and in the OS) and second you'll need to figure out how to
change interrupts in your OS (if necessary).

FWIW here is the manual for your board:

ftp://download.intel.com/design/motherbd/nt/D1406901US.pdf

Page number 52 and 53 is where it talks about interrupts.

 

[George Macdonald]

It would be largely dependant on several features. The BIOS and the
OS both have a big hand in this and whether they are using APIC or the
legacy method of doing things will affect things a lot.


Those are some *very* poorly written drivers!


Is your OS APIC aware? if so than it is the OS and not the BIOS that
will have the final say in how the interrupts are allocated.

Hmm.. it looks like this 'iRMX' thing is a Real Time OS for Windows?!?
Ugg! No wonder the thing has so many problems! :>

Not really - iRMX was probably the first OS for 808x chips, written by
Intel for its industrial computer MultiBus systems. It's been through a
few transformations over the years, Intel's last effort being iRMX for
Windows 3.1 in 1992. Tenasys, which claims to still have Intel
ex-employees around, did a modern version which kicks Win(whatever) out of
the way as a low priority task, and takes over the machine.

 

[Ultra5]

You are right George, iRMX was originally by Intel and was then sold to
RadiSys and then sold to Tenasys. They still offer iRMX as a stand alone
operating system (http://www.tenasys.com/irmx3.html) as well as a
'real-time' addition to Windows. We use iRMX III as a stand alone operating
system on PCs as well as an older version of iRMX in some of our embedded
platforms. All of our iRMX based stuff had it's start in MultiBus (well
before my time).

I am not sure if the non-windows based iRMX is APIC aware or not, I doubt
it. But I will check it out.

 

[George Macdonald]

You are right George, iRMX was originally by Intel and was then sold to
RadiSys and then sold to Tenasys. They still offer iRMX as a stand alone
operating system (http://www.tenasys.com/irmx3.html) as well as a
'real-time' addition to Windows. We use iRMX III as a stand alone operating
system on PCs as well as an older version of iRMX in some of our embedded
platforms. All of our iRMX based stuff had it's start in MultiBus (well
before my time).

Interesting. Is the standalone version now 32-bit paged mode?

I am not sure if the non-windows based iRMX is APIC aware or not, I doubt
it. But I will check it out.

No luck on "exposing" the full BIOS Setup? Some mfrs certainly have key
combos which unlock hidden details, e.g. with MSI it's Shift-F2 followed by
Alt-F3; with others it's Ctrl-F1. Let us know how you make out.