[comp.sys.dec] DECsystem 5800 with 2 processors slower than with 1?

mf@ircam.ircam.fr (Michel Fingerhut) (09/26/90)

We noticed a significant slow-down of our 5820 (bi-processor 5800) in
response time after upgrading from Ultrix 3.1 (which supports a single
processor) to Ultrix 4.0 (whose "kernel has been enhanced to support
multiple processors executing kernel code").

The local DEC support's reply to my call was that it was a known
"problem" and their advice was to turn off the  2nd CPU until a fix is
found.

I did this, and lo and behold, "ls" runs so much faster... I wonder if by
turning the remaining CPU off I'll get the computing power DEC claims for
the DS5820.

rosenblg@cmcl2.NYU.EDU (Gary J. Rosenblum) (09/27/90)

I haven't had that problem on my 5820 with Ultrix 4.0.  I timed an
ls in a HUGE directory with both cpu's on, and then with one off,
and the times were comparable.

Did the DEC people give you any indication as to the problem (or a
patch to 4.0?)

					Gary

ndoduc@framentec.fr (Nhuan Doduc) (09/27/90)

In <1990Sep26.151338.14480@ircam.ircam.fr> mf@ircam.ircam.fr (Michel Fingerhut) writes:
>....
>I did this, and lo and behold, "ls" runs so much faster... I wonder if by
>turning the remaining CPU off I'll get the computing power DEC claims for
>the DS5820.

You have 2 proc. you shut off 1 and get (my interpretation) twice (faster)
My deduction is that if you shut down the remaining then the computing power
would be infinitely faster.
Hey look at this: 1 / half = twice
                  1 / zero = infinity
CQFD

--nh
Nhuan DODUC, 
Framentec-Cognitech, Paris, France, ndoduc@framentec.fr or ndoduc@cognitech.fr,
Association Francaise des Utilisateurs d'Unix, France, doduc@afuu.fr