[HECnet] LSSM group visit today

[Johnny Billquist]

On 2021-11-16 19:20, Dave McGuire wrote:
> On 11/16/21 1:05 PM, Johnny Billquist wrote:
>>>    Speaking of ddb, does it do a DTR query across the network to 
>>> access the data?  Or something else?
>>
>> Yes it does.
>> Sources are on MIM. See
>> MIM::HECNET:DDB.C
>> and
>> MIM::HECNET:DDBDTR.CMD
>>
>> (Yes, DDB itself is written in C.)
> 
>    Very nice, I will look at it.  I've been wanting to learn Datatrieve 
> programming.  Thanks for the source!

It's fairly simple, if a bit stupid.
You can see an older version of the Datatrieve code inside the C file, 
but a more up to date version is in the CMD file.

The C code also make use of a C library to access the DTR call 
interface, making it a bit easier to use than the standard interface DEC 
defined.

>>>    It sounds like MAGICA is much bigger.  We don't yet have a Unibus 
>>> expansion chassis connected to FANG, so we have limited Unibus slots. 
>>> There's an RL02 and an RX02 in its rack, but no place for their 
>>> controllers to live.
>>
>> What? You only have the four slots in the CPU backplane? That's a 
>> rather unusal and limited 11/70 setup.
> 
>    Yes, I removed the BA11-K expansion chassis when I got that system 
> many years ago.  The system was going into my house, years before I ever 
> knew I would be able to finally realize my dream of opening a big-iron 
> museum, and the only thing in the expansion chassis was a DH11 and a few 
> DZ11s, and that chassis was the only thing in that extra rack.  So, 
> needing to reduce its size and power consumption for a home environment, 
> I removed that chassis and rack from the configuration.  That was about 
> twenty years ago.  The DL11-W, UDA50, and DELUA are currently the only 
> Unibus peripherals on FANG.

An extra RL02 is almost invaluable. We do crash dumps on it, we run 
diagnostics from it, we can easily move files to/from it on the RL02 and 
so on...

And the tape drive is nice for backups, software installations... 
Although nowadays with virtual tapes, the tape drive isn't needed that 
often. A long time since the last RSX release came around. :-)
TU81 is 1600/6250. So from time to time we have hooked up a TU77 as 
well. But the status of those drives are a bit unknown today.

But occasionally we also get requests for media conversions... For that 
purpose we also did plan for quite a while to hook up an RK11 and RK611 
to Magica. But now I think we'll have to scrap that plan.

>>>    We also have an Emulex SC72 disk controller (actually a few of 
>>> them), which is a board set that plugs into RH70 slots and implements 
>>> an SMD interface.  We have a Fuji Eagle prepped and ready to go onto 
>>> that, but we still need to cable it up, format it, etc.  I expect 
>>> that to be much, much faster than the UDA50+RA73.  Hopefully we'll 
>>> get to that sometime this winter.
>>
>> That could potentially be much faster, yes.
>> I haven't done any tests, but I suspect even some SCSI on the 11/70 
>> and some modern disk would be a big improvement. I think seek times on 
>> the RA73 isn't that great.
> 
>    Before we got the RA73s, I was running an Emulex UC17 and a 200MB 
> SCSI drive on that system.  I didn't do any tests either, but I think 
> the bottleneck was the Unibus; the UDA50+RA73 doesn't really feel any 
> different.

I would like to test something with SCSI one of these days.
I have SCSI on my 11/93, and CPU wise the difference isn't that big 
compared to Magica, but pure disk I/O operations difference is huge.
Sure, Qbus is a bit better than Unibus here as well...

But it just feels like seek times is playing a big part.

>    That UC17 is now on my personal PDP-11/34 at home, connected to two 
> Bernoulli 44MB drives.  I make disk images under simh, and dd(1) them to 
> cartridges to run on it.  That 11/34 has no network interface, so it's 
> not on HECnet, but I do run it occasionally, for soul-healing purposes. 
> I may try to network it at some point.

I sortof don't like the 11/34 that much. Boring front panel (if you even 
have one), and limited capabilities. :-)

>> But the Unibus on the 11/70 is also known as possibly the slowest 
>> Unibus around.
> 
>    Yes, that's why we'd like to move our mass storage away from that, if 
> we can make it all work.

Plugging something into the RH70 slots is definitely tempting...

The one other big thing on the wish list for any 11/70 would be a 
PEP-70/HC-70 combo...

   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