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Avid Exp chassis bus division


Active Member
Does any one know what the specific bus layout is in an avid 32bit/33MHz 7 slot pci exp. chassis (flat cable)?

I think I've heard 4 slots share a bus and three more share another but what's the breakdown/slot numbers?
At present I have mine set up with:
Host card, empty, empty, tc poco mkII, empty, empty, UAD-1,UAD-1.

UAD cards work great but use of the TC occasionally causes ProTools (7.2 HD2) to drop connection with the TC and UAD plugs until I close and reopen the session.
When PT drops communication the UAD meter and the PoCo utility both maintain connection to the cards so I believe it's more of a PT issue but Digi doesn't support either so I'm left to hunt and peck for a solution on my own. I thought playing with the card order might be a place to start.



Active Member
I have a Magma 32/33 old school with the flat cable with 3 UAD cards, on a native system though running Sonar. I have my cards in slots 1-3 ... it all goes to one PCI slot, so could there really be more than one bus in the chassis?

Perhaps is it the default power supply in the chassis? I upgraded mine to a silent psu just for the hell of it and haven't had any issues.


Active Member
Perhaps \"bus\" is the wrong term for what I'm asking. It's just that I vividly remember posts about a difference between 4 of the slots and the other 3 and I can't locate the info now that I may need it.


I remember that nobody knew for shure. I think it's supposed to be using 3 or 4 different IRQs for every 3 or 4 slots.

1 2 3 1 2 3 1
1 2 3 4 1 2 3
something like that...

Maybe you should just try different setups.


Sadly, left this world before his time.
The IRQ sharing in my system is like this:

Slot: 1 2 3 4 5 6 7
IRQ: 17 18 19 16 17 18 19


New Member
Akis said:
The IRQ sharing in my system is like this:

Slot: 1 2 3 4 5 6 7
IRQ: 17 18 19 16 17 18 19
Hi Akis!!

just 2 questions:

you are running xpsp2 in acpi mode?

does a pci-e card use an irq just like a standard pci card?
If right the pci-e card share the same irq of a pci bus, doesn't it?

My B.


Active Member
Thanks for the info.
I guess I'll try the IRQ list as a guide and move the PoCo to a different slot so it doesn't share the same IRQ as one of my UAD cards.......
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