guest (06/10/82)
I'm working with some folks who have a tricky problem. Maybe
someone out there can give us some clues? Here's the story;
Our hardware is as follows- PDP-11/44 with 512K RAM
Two CDC 80 Mbyte drives
(emulating RM02)
Plessy PM1102 disk controller
We're running straight 2.1 UNIX/v7 (2.8bsd is coming soon).
Everything is fine as long as we use only one drive, but if we try
to go with both drives it seems like all processes become blocked as
soon as they try to do disk I/O. Thus everything just sort of freezes
up. You can unfreeze things by toggling the start switch on one of
the drives on and off. Oddly, you can write from one drive to the
other using 'dd' sometimes (sometimes freezes up!) but if you try
to mount a filesystem on the second drive everything hangs.
The Plessy diagnostics work fine, and either drive will work
by itself. We suspect that UNIX is not catching an interrupt(s) from
the drives and won't proceed without it. DEC sells a similar arrangement
with their own controller. They modify the drives for their setup, and
actually slow down the rate of spin on them.
Has anyone else seen this problem? Is anyone else using the
PDP-11/44 with these drives? Suggestions? Clues? Help!