QBUS SCSI card...

From: Zane H. Healy <healyzh_at_aracnet.com>
Date: Mon Feb 24 23:28:00 2003

> 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

> 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 :^)

Received on Mon Feb 24 2003 - 23:28:00 GMT

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