TALOS is back online :-)

Chris Zach cz at alembic.crystel.com
Mon Dec 30 15:52:49 CST 2019

Well, I've been working on all these RL02 drives and such in an effort 
to repair the pdp11/73 that I used to bring to science fiction 
conventions in the 1980's and 1990's. TALOS was the new system, BALCON 
(after Balticon) was the older system that ran on RL01's and would 
require me hauling a 6 foot rack of gear in a 1971 station wagon. Oh 
those were the days, splitting power with the laser frobs and running 
multi-player games back in the late 80's....

Anyway, Talos suffered a failure a long time ago and has been dead 
since. Now that I have time and space I've been working on fixing it. 
First step was to find out if anything worked, turned out one of my RL02 
controllers was flakey and one of my RL02 drives had a very naughty head 
that resulted in the destruction of my RSXM38 boot pack. And the memory 
was unhappy. But the 11/73 CPU was sound.

After fixing that junk I was able to boot RT11 and install it on one of 
the partitions of the Fujitsu ESDI disk (MTI controller, has two 
partitions per disk each about 70mb in size). So finally the system and 
drive logic was working but trying to boot the RSX11M image just gave me 
a trap to zero fault.

First step was to fix a RSX11M 4.2 system disk. Did a quick sysgen on 
SIMH, built to a RL02 pack image, then once that was up and working with 
DU: driver support (the out of the box disks do not support DU:) I was 
able to transfer the image over serial using pdp11GUI (great tool!) to 
the RL02 drive. Now I could boot RSX11M on the RL02. However I knew that 
I had only one shot to fix the Fuji drive, and I wished I had a backup.

Wait! I can make a backup of the Fuji drive using PDP11GUI! Upped the 
baud rate on the 11/73 from 9600 to 38400, loaded the drivers, fired it 
up, and let it run for 7 hours to copy the disk image. Really 
interesting that there were no errors, meaning the disk image itself was 
not the problem. Hm....

Then I made a copy on my laptop (took less than a second, sigh) and 
realized I could boot the RSX11M image on SIMH *and* mount the Fuji 
volume copy to find out what was up.

Booted the image, mounted the disk, and took a look. Found it pretty 
quickly: Back in 1997 I was doing a cleanup of the system and did a 
purge of old versions of files in [1,54]. I must have had a later 
version of RSX11M there from a VMR operation that I never committed to 
disk, and when I purged the older version it was the one that the boot 
block was trying to reference. Thus the system ran fine but when I shut 
it down and booted it a few years later it could not find the deleted 
file and crashed out.

Simple. Solution was to set the default to DU2:[1,54], then boot 
du2:rsx11m, hit G when the XDT debugger came up, then type SAV /WB to 
re-write the boot block with the correct version of the RSX11m file. 
Sure enough, the system booted up, complained about not finding the 
DZV11 cards (I had removed them for testing) and was working. Shut down 
the RL02 drive, did a cold restart, and TALOS came up and online :-)

Now I need to figure out what to do with it. I think it has DecNet 11/M 
4.0 on it, so I could do a Phase II link with another system over serial 
ports/tcpip to serial gateways. If I can find the later versions of 
Decnet 11/M I could probably gen an Ethernet card and do a gateway to 
TCP/IP systems. Anyone want to peer with this old system?

Overall this was an interesting little project: It required me to dust 
off my hardware, software, and OS level troubleshooting skills. Now that 
the system is up I can start working on hooking up the RX01 drives to 
get the PDT11/150 some fixed disks, then start thinking about the 20/20 
core in the shed.....

Never dull, and thank you everyone for the help and the tools.

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