24 Feb
2003
24 Feb
'03
3:28 p.m.
I'd say it's more the difference between the
throughput of the DEQNA
and the throughput of the RQDX3/RD54 than it is between the difference
between MFM & modern SCSI. My fileserver will spew data a good bit
faster than the DEQNA can process it. The Qbus ethernet is the
bottleneck.
I'm pretty sure you're right about the DEQNA being the bottleneck. Have you
clocked the throughput on the DEQNA? I'm guessing it's about 1Mbyte/Sec max
(in reality I'd guess it's FAR lower). IIRC, the Q-Bus can only handle
3Mbyte/Sec. I think all the memory ops go over the ribbon cables (isn't
the q-bus limited to powering the RAM, it's been a 2-3 years since I looked
at a Q-Bus VAX and my memory stinks at times) so you should have a mostly
free pipe between the DEQNA and the CPU.
It would be interesting to have a Q-Bus FDDI adapter (DEFQA) and see how much
more performance you could get using it, since it will saturate the Q-Bus.
I think I'll have to look into seeing what it would take to set up such a
test.
No hurry, anyhow. It's mostly academic to me -
the whine of the MFM
drives makes SWMBO nuts. The choice to go network-based storage had the
unexpected speed boost, but peace in the castle was/is the overriding
factor....
My wife doesn't know how lucky she is that I had my PDP-11/73 in the BA123
in basically it's current condition when we got married. She never had to
experience it without all the panels and MFM or ESDI disks :^)
Zane