[Simh] Dec-10 Day announcement from Living Computers: Museum + Labs

[Johnny Billquist]

On 2017-12-11 23:36, Rich Alderson wrote:
>> From: Johnny Billquist <bqt at softjar.se>
>> Date: Sun, 10 Dec 2017 11:12:45 +0100
> 
>> Rich. This is a nice thing. Thanks.
> 
> Thanks, Johnny.
> 
>> I have one question/wish, though.
> 
>> I don't know if you were aware of a device called the RM06. This was a
>> Massbus disk created by Shelby, which was varible size.
> 
> I am not familiar with the RM06, which was not supported under Tops-10 or
> TOPS-20.  The MDE started out as a replacement for the RP06 drives on our
> DEC-1080 (replaced by the DEC-2065 on which we offer on-line accounts).
> Because other operating systems for the PDP-10+Massbus only supported
> the RP06 or RM03, we did not look beyond those for our own needs.
> 
> I was disappointed to learn that the RM05 was never supported, either.

Hmm. Yeah, I can't remember ever seeing 18-bit packs or support on the RM05.

The RM06 is not that well known, so I'm not surprised if you didn't know 
about it.

>> It would be a really nice thing to emulate. I can probably reverse
>> engineer it from the RSX driver, and I don't know which systems ever
>> supported it. RSX for sure. Possibly also RSTS/E, but beyond that is
>> more uncertain. Most people and systems had moved on from Massbus before
>> this drive came out.
> 
>> But it is a much nicer solution than emulating eight RP06 drives, when
>> you have some big disk in the backend.
> 
> Not if the OS doesn't support the big disk.

True. But if you do have the support, then it is much nicer. As with 
everything, it's not a universal solution, but yet another solution that 
under some circumstances can be better.

And since it did exist, it would make more sense than doing something 
from scratch, if something similar were to be considered.

And it would be nice if support could be added to other operating 
systems than RSX as well. It's not actually that complicated extension, 
as far as I can tell.

>> Do you know what speeds this emulated massbus disk can achieve, by the way?
> 
> Fast enough to supply 8 RP07s on a KL-10 based Dec-10.  We haven't done any
> serious benchmarking; it's good enough for our needs.

So I would assume it at least performs similar to a real RP07, which is 
nice. Seek times will obviously almost always be better on todays disks. 
As long as transfer rates are acceptable, then this is a very 
interesting improvement.

Me thinking right now if this wouldn't be a nice project for 
Magica.Update.UU.SE (PDP-11/70 running RSX). The RA73 disks are really 
the slow part of that system, compared to a system I have at home with 
SCSI disks. We certainly have RH70 adapters just sitting there, and for 
the 11/70, this could be a serious improvement in performance compared 
to an UDA-50.

   Johnny

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