QBUS SCSI card...

From: Zane H. Healy <healyzh_at_aracnet.com>
Date: Tue Feb 25 13:01:00 2003

Brian Chase wrote:
>On Mon, 24 Feb 2003, Zane H. Healy wrote:
>-> On Fri, 10 May 2002, Anders Magnusson wrote:
>-> > You can look at the original DEC driver that were in NetBSD, it
>-> > have some of the compensation code for bad DEQNA's. Note that the
>-> > DEC driver is quite slow; it could almost reach 200k/s (in both
>-> > directions). The new one I wrote peeks about 500k/s.
>I was seeing something close to 500KB/s on my systems, too.

Truth be told, that's actually a bit better than I was hoping for.

>> 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.
>Another thing to keep in mind, IIRC, is the position of the modules
>along the Qbus chain.

Good point, I believe you're right.

>> 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.
>Ouch. I bet that'd be pretty painful for something like a MicroVAX-II
>class machine; still, I'd love to see it done!

Does the FDDI controller load down the host systems CPU, or does it handle
the load onboard? It doesn't really matter, after a little research, I
don't think I'll be testing this unless I happen upon a really cheap FDDI
controller, it looks like they're more than I can afford to spend on a
something that would be to simply satisfy my curiousity.

| Zane H. Healy                    | UNIX Systems Administrator |
| healyzh_at_aracnet.com (primary)    | OpenVMS Enthusiast         |
|                                  | Classic Computer Collector |
|     Empire of the Petal Throne and Traveller Role Playing,    |
|          PDP-10 Emulation and Zane's Computer Museum.         |
|                http://www.aracnet.com/~healyzh/               |
Received on Tue Feb 25 2003 - 13:01:00 GMT

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