PV220S Split bus Issue

[David Brain]

I'm trying to connect two machines to a PV220s.  I have the PV 
configured in split bus mode.

Currently connected (and working) is a 1650 using it's internal 
(non-RAID) controller using the first 7 drives.  I'm attempting to 
connect a 2nd 2650 with a PERC3/DC to the second half of the tray - 
however it doesn't detect the enclosure.  No drive lights flicker during 
detection, and the external drives don't show up in the BIOS config 
tool.  Both PERC and cable were tested and confirmed working on a 
separate PV.

The only thing I've found in the Dell docs is this:

"""In either case, it is highly recommended
that both halves of the PV22xS be connected to the same type of SCSI 
RAID controllers
(e.g. PERC4 and PERC4 or PERC3 and PERC3)."""

Now in this situation this is not the case - but it's not clear to me 
why this would matter if the buses are isolated.

David.