On Wed, 30 Jul 1997 13:52:37 EDT, John Archer <[log in to unmask]> wrote:
|I currently have 6 HPIB drives on one channel (947). I seem to remember
|that HP recommended not to go over this limit. Is this correct or was
|that the SCSI channel?

As I recall (It's been a few years....), the performance recommendation used
to be 3 drives per HP-IB channel, but that was before the PA-RISC machines
which typically have lower disc I/O bandwidth demands, assuming ample memory
is available.  Disc drives (and many other devices) are considered
"high speed" for the HP-IB bus.  "Low speed" HP-IB supported 8 devices, but
a high speed HP-IB bus (one having one or more high speed devices) supports
a max of 6 devices.  However, the HP-IB spec seems to be HP's (former?) usual
conservative worst-case design.  I have personally seen systems with 8 very
active disc drives on one card with no apparent problems over long durations.
I suspect that the risks were increased that I/O errors may have occured and
that the drives were running at less than optimum total throughput, but it
worked.  It simply isn't "supported".  :)

BTW, HP-IB is an amazingly robust interface.  I have seen the cabling
requirements for it extremely abused (ignored would be more accurate) and
it still work.  Of course, I have seen it fail several times too, where
"fixing" the cabling a bit by making it slightly closer to the requirements
corrected the problem.
--
Jeff Woods
[log in to unmask] at Unison Software
[log in to unmask]   at home  [PGP key available here via finger]

"There ain't no rules around here!
 We're trying to accomplish something!"  --  Thomas Edison (1847-1931)