eagle

[irwin at uiucdcs.UUCP]

We are running 9900s on nine machines, 2-780s and 7-750s. The 780s have
SBI interfaces on the mass buss, the 750s have CMI, so none are on the
unibus.

When we got the systems, we could not hack the cost of maintenance on
all nine, so elected to handle the 750s ourselves. The 9900s on the
780s have been kept at current rev level, the 750s have not as a result
of no maint. Our 780s are on DEC maint, but not the 750s.

The firmware in the 9900s on the 780s is a 4 rom set (level 6.2 I think
and handles bad block forwarding without special drivers) but we put in
a patch for the bbf under 4.2 and have not changed it since the latest
firmware was installed in the 9900s. I am told that level 7.0 is just
around the corner.

The firmware in the 9900s on our 750s is a three rom set, and we have
had disk files damaged on those systems. We just went through a rather
lengthy negotiation with SI to get the 750 disk sub systems on maint,
so that we can get them up to current rev. I do not feel that the bug
will remain after we have done so.

We have been pointing the finger at SI because we were having problems
with the 780s, they would go off into never-never land, no error messages
and we could not determine what was causing it. SI helped us locate it,
by studying the register dumps that we took. It turned out that we had
some soft mem errors (which we knew about but ignored because they were
correctable, were brand X, not DEC memory) and the memory controller was
getting a second error while trying to correct the first, so "hung buss"
by a confused mem controller. Now that we have cleaned that up, the 780s
have not been causing problems. We got our 780s with 4 meg (256k boards)
and later added an extra cabinet to one, moved the 4 meg to it and got a
8 meg mem for the vacated memory hole in the other. That one was the one
giving us the most trouble and DEC mem tests on their micro diag floppy
#3 for the 8 meg unit would not even report any errors. The #2 floppy
which covers the 4 meg mem unit does a very complete test and points out
any bad boards.

If you have a choice of unibus or CMI or SBI, I would recommend avoiding
the unibus controllers. We had them before changing over, you will get
better through-put on the mass buss. We did not have problems with the
unibus controllers (ours was Emulex) but a lot of swapping and so on can
sure load down the unibus. We are running 96 RS-232 ports on each of the
780s on Emulex H2 unibus controllers and average 30 to 45 users logged in
at any one time on both machines.

I hope that this information is helpful.

--al irwin--