2nd Classicboard SCO 5.0.6

Is it possible to add a 2nd classicboard to work with SCO 5.0.6.
I am working on a Compac ML330 system
I can get SCO to see either board 1 or 2 but not both.
I have gone into setup & disable the onboard COM2 port and gone into PCI setup and forced the irq of one of the classicboards to irq 3 (the other deflauts to 15).
I have gone into mkdev serial & deleted the original COM2 and tried every combination of adding the 2 boards but all to no effect.
with both boards configured all I can ever see is board 1. if i delete the configuration for board 1 then I can see board 2.

anyone with any ideas?