Re: DSSI and VAX 4000-200

[Johnny Billquist <bqt%update.uu.se@localhost>]

On 2021-01-16 02:47, Charles Dickman wrote:
> I used a KFQSA and an RF71 with a PDP-11/73 on BSD2.11 for a while and 
> it worked fine. I used a KA655 with it for configuration. The drive has 
> its own console. Very cool when I first saw it.

Cool. I almost suspected it should work, but I have never heard anyone 
before who actually tried it.

> My research on KZQSA is that it is SHAC controller with the sector 
> buffer on the Qbus. My understanding is that SHAC controller is DSSI and 
> SCSI controller. There is information in some VAX manual (KA660?). I 
> speculate that DEC said the controller was no good for disks because the 
> performance would be so bad. At this point no open source drive exists 
> for it either.

And since there isn't even any documentation at this point, it's 
unlikely to write a driver right now. So it's mostly useless.

> I have never heard anyone admit to having a RQZX1. They must be very 
> rare, but as a DEC supported MSCP Qbus SCSI adapter it must be good.

I have one. And I know some companies who used/use them. I actually 
haven't tested mine, since I have CMD controllers as well, which I'm 
already using.
But at some point, I should take it for a spin.

I seem to remember reading once somewhere that the CMD controllers are 
better than the RQZX1 when it comes to performance.

> I have used CMD and Viking SCSI controllers with much luck and there are 
> SCSI to ATA adapters that let you use modern ATA drives.

I use CMD with fairly modern SCSI drives. Also works just fine. Just 
need an adapter for the connector.
However, >8GB drives just get capped at 8GB for RSX. :-)
(Not using SCSI any Qbus or Unibus VAX.)

  Johnny

--
Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt%softjar.se@localhost             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol