A clarification... I think that there is some confusion going on here about
what the connection and configuration limits for SCSI are.  If my
understanding is correct, the SE SCSI limit on the number of address values
is NOT the same thing as the limit on the number of physical devices.  Again,
if my understanding is correct, ONE SE SCSI address value can have up to 8
subsidiary unit numbers (aka: "LUN" for Logical Unit Number)

Steve Dirickson wrote that the SE SCSI device limit is 56.  I beleive that he
is correct as 7 possible target address values each with 8 units equals 56.
You could claim that the limit is 57 if you count the SE SCSI
adapter/controller/interface as a device as well ( 56 + 1 = 57).

SCSI is in many many ways very much like HPIB.  For HPIB, in the non-HP-3000
HP world (ie: older HP workstations and such), it is very common for a single
HPIB address to have a number of different unit numbers setup.  These unit
numbers might correspond to devices but could also be seperate partitions on
a single disc drive.  Does anyone remember the HP-150-II which was used as a
system console on Series 64/68/70 machines?  Those 150-IIs had a seperate
dual 3.5" floppy cabinet which had ONE HPIB address and TWO unit numbers -
one for each floppy disc mech.

Note: Just because the 56 devices are possible using SE SCSI, that does NOT
mean that all operating systems, software, etc utilize unit numbers and since
many devices only have a means of configuring their address and no way of
specifying a unit number, practical configuration limits will be far less.

Wayne Boyer

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