VAX 750 disk controllers

[utzoo!decvax!ucbvax!unix-wizards]

>From decvax!duke!unc!lynn at Berkeley Sun Dec 27 16:02:41 1981

We have two SI 9400 Unibus disk controllers on VAX 780's.  I would not
but them again.  For about eight months we had endless problems finally
fixed -- we were getting noise on the reset lines which would terminate
transfers and also clear all error bits (and vv, and mol).  After many
board swaps (you thought DEC field service was bad that way!) the problems
were finally fixed (probably noisy power supplies) but I would not be
willing to go through that again.  In addition, the SI controller does
not keep up with the disk on a 780 -- I don't know about the 750.  This
is not a serious problem, as all file system transfers are fully buffered
in the controller, but does cause some performance loss under heavy
swapping.

I strongly recommend that you look at two other disk controllers -- the
Western Peripherals DC-231 and the Emulex SC-21v.  Both are single board
Unibus controllers that are known to work on the VAX.  Personally I think
the DC-231 is a shade better, but I am biased -- I consult for Western
Peripherals.  (There is both Unix and VMS support for both controllers,
by the way.)  I think the Emulex is $5000 and the WP is $3500, but check
it out.

You might also look at the Xylogics 650 -- they have an RM02 emulation
and an RK07 emulation, which might be of interest if you plan to run
VMS.  (Software transparent, but not as nice a configuration.)