21 Apr
21 Apr
4:57 p.m.
Here's a question: What's a KFQSA?
That would be a Qbus DSSI controller. I have one in my MicroVAX
3800. I know just the bare minimum about it to have my system
working, unfortunately. I believe the disks are controlled with
MSCP over DSSI. It can also be used as a Cluster Interconnect
on VAXen (don't know about qbus PDP's -- it's sadly been far
too long since I played with any PDP *pout pout* :)
The KZQSA is the board I'd really like to have -- it's the QBus
SCSI controller cousin of the KFQSA, and I'd finally be able to
hang a SCSI tape and perhaps a spare disk off my MicroVAX.
-Seth - PDP lover who has too many VAXen and no PDPs :)
5:12 p.m.
[No PDPs...]
Where are you? I have a load of PDPs, but I've been hunting for a Q-bus VAX.
I have a 23+ I can let go of, but you'd need something to boot from.
It has an EDSI controller I'd like to keep.
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22 Apr
22 Apr
3:51 a.m.
By the way, What's DSSI?
Well, it appears to be Yet Another variation on SCSI, but with more
Oomf. (how's that for a really clever way of admitting "I don't know
the protocol details"? :)
Seriously though, it's both a disk bus and a host interconnect for
VAXen. I don't know if PDP's ever used DSSI, though I imagine they
probably did.
Each DSSI disk (RFXX series DEC disks) has a complete "host" built
into the on-disk logic board. The disk firmware acts like a little
tiny host, for sharing in a cluster for instance, or for just
talking to the KFQSA controller. This allows each RFXX disk to do
low-level sharing in a cluster, handling requests for disk access
from remote hosts without relying on the VAX host to
take care of
processing them, apart from handling the Ethernet<->DSSI bridge
if
Ethernet is being used as the cluster interconnect.
You can also connect two VAX computers directly together over a
DSSI bus, using an external DSSI cable.
On a VAX, you can do this at the console ROM monitor:
>> SET HOST/DUP/UQSSP/DISK 0
Upon hitting <enter>, you are connected to the on-disk firmware
of DISK 0, where you can perform diagnostics, change firmware
settings, format the disk, run tests, and so forth. Really quite
neat. I'm sure other disk connections do this, but DSSI is the
only one I'm familiar with.
Anything else out there like this?
-Seth
9858
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