8 Dec
2013
8 Dec
'13
6:22 p.m.
Some of this you might know, but I learned it by trial and error. The MSCP
disk unit numbers are unique across all controllers and need to be set on
each controller. If the unit numbers on different controllers are the same,
it might not be possible to boot from the second controller. It appears
that the boot ROM will search each controller to find the first instance of
the specified drive.
2.11BSD limits a disk number to 3 bits and so only DU0 through DU7 can be
addressed by 2.11BSD. For 2.11BSD duplicate unit numbers on different
controllers are OK.
I have two controllers with DU0 - DU3 (SCSI) on the first controller and
DU4 and DU5 (RX50) on the second. This was the only way that I could have
the RX50 bootable and visible from 2.11BSD.
All this said, I don't know that it explains some of what you are seeing
because MSCP disks and tapes are in different unit number "spaces" and DU0
and MU0 wouldn't conflict.
-chuck