Thanks very much Andrew.
I have been finding out some of these details bit by bit, but glad you've confirmed my suspicions about how hard this will be. I was hoping I'd missed a trick but it looks like I will have to delve into the BSP and drivers to partition the IRQ lines between the processors.
This is probably more trouble than it's worth, as we have room to simply put two crates in if we need to.
I'm trying the intermediate solution of offloading some of the CPU intensive work to the second processor without shifting any of the I/O. This will put a lot more strain on channel access but the traffic will go through one local switch, so may be OK.
Thanks again.
Keith