• Please review our updated Terms and Rules here

Reviving the PDP-8/I at the RICM

What is/was Warren doing that you weren't? Did the problem resolve down to flow control for the larger files or was there some more insidious issue?

The H-11 is fun but you can also format RX01 floppies on a DOS system with John Wilson's FDADAP 8" drive adapter and PUTR, probably a more robust solution since it can also function as a diskimage workstation.

Jack
 
Hi All;
M-Thompson, "" This system contains a DEC LSI-11/03 processor and Heathkit I/O boards "" I think I have the same machine.. Mine has a floppy, (third party), I might have some floppies for it, but I would need to find mine and I don't know even if my floppy Controller works..
I have another board for it, but that board doesn't work, as far as I know.. So, I would be looking forward to Your exploits with Your Heathkit machine..

THANK YOU Marty
 
jackrubin said:
What is/was Warren doing that you weren't? Did the problem resolve down to flow control for the larger files or was there some more insidious issue?
Jack
Click to expand...

I am not sure what the issue is. Warren made a current-loop to RS-232 adapter for us which includes the reader run signal. We connect reader run to CTS on the RS-232 side. We turned on RTS/CTS flow control in the terminal emulator. We tested the flow control by halting the processor while it was in a loop reading characters, so we know it works. We set the serial port FIFO in Windows to just 1 character. It looks like Windows sends a few characters after CTS turns off.

The Classic PDP-8 that Warren is using has a custom made PIC based serial interface, so maybe that works better than the DEC interface that we are using.
 
We removed, cleaned, and polished, and reinstalled the tape guides from the third TU55 DECtape. The brakes would not go on when the drive was in LOCAL or REMOTE. We eventually found that the DELAY output from the R303 in slot A04 never changes.

R203.jpg

The R303 was covered with corrosion, so that may have had something to do with the failure. We swapped the R303 from the second drive, and the brakes now work. The borrowed R303 was also covered with corrosion. We borrowed another corroded R303 from the fourth DECtape drive. After cleaning the R303 module, and the rest of the modules in the drive, the brakes on the third DECtape drive work.

We booted DMS from the first DECtape drive, and installed another DMS tape on the third DECtape drive. We can read the directory from the third DECtape! Well, it wrecked the tape when we wrote to it, so there is still some debugging to do next week.

Warren sent us paper tape and DECtape images of DECUS-8-195 POLY BASIC. This version of BASIC should boot from DECtape, and load and save programs from the DECtape. It should also run on this 4k 8/I.
 
Last week we wrecked a DECtape on drive #3 when we ran DMS from that drive and tried to write to it.

This week we loaded the MAINDEC-08-D3BB-D TC01 Basic Exerciser with a previously formatted DECtape.
The Basic Motion test works, so at least the motors and brakes are OK.
The Search Scope Loop displays all of the blocks in the AC.
The first tape that we used had a bad spot in the middle, so we are using one from a PDP-11.
I don't want to wreck one that we formatted on this system.

The Search Find All Blocks works, but always displays an error message at the end of the tape.
SEARCH FWD
1102
1101
5000

This is because a PDP-11 DECtape has less blocks than a PDP-8 DECtape.

We reformatted the tape on DECTAPE drive #3.
Formatting didn't work last week, so maybe exercising it with the diags made it work better.
We used DECtape Copy to copy a DMS tape from drive #0 to drive #2.
We changed the drive numbers so that the top left drive was #0, and rebooted DMS.
DMS started right up and seems to be working OK.
We will declare all three DECtape drives functional.

So, it looks like all that is left to do on this system is fix the indicator lights on the TC01 DECtape controller.
We need to make a POLY BASIC DECtape from the image that Warren sent us and add some demo programs.
We need to print boot and run instructions so anyone can use this system for demonstrations.
 
m_thompson said:
Mattis,

There is a video of DMS booting here: https://youtu.be/SWYaKCNW-8A
You can't really see the tapes moving.
We later put some black tape on the take-up reel so it will show up in the videos.
There is a video of DMS doing a tape copy here: https://www.youtube.com/watch?v=HyH23t1KkEk
Click to expand...

That was really nice to see them run for real! So how long does it take to copy an entire tape?

The DMS for dectape is mostly the same as the one for DF32, right? I have a thick roll of paper tape that says Disk Monitor DF32 for my PDP-8. Maybe it is possible to run it if I get the DF32 working.
 
There are some minor differences for PIP and DDT, but they are otherwise the same.
The DF32 monitor can be built to span multiple DF32/DS32 drives.
We can post an image of the DECtape that we are using so you could use dumprest to make a real DECtape.
The DMS paper tape images are available if you want to build a DECtape from paper tape.
 
We booted DMS (nice to have the processor still working for a few months) and formatted four DECtapes from the collection in the warehouse. These tapes didn't have a directory listing in the container, and said DATA on the label. There are a bunch of DECtapes with RT-11 directory listings in the container that we will preserve, and eventually make images of them.

We use the BIN loader to load the DECUS-08-195 POLY BASIC loader, and then fed it the DECUS-08-195 POLY BASIC SYSTEM tape. After about 25 seconds the Reader Run signal turned off, so CTS on the serial port turned off, so the terminal emulator stopped sending data, the POLY BASIC loader wrote a little of the BASIC SYSTEM on the DECtape, then the Reader Run signal turned on, so CTS on the serial port turned on, so the terminal emulator started sending data again. This cycle repeated for about 30 minutes, and then it printed READY on the console. There was a blinky light pattern in the AC when the system was waiting for input. We were able to write a little BASIC program and save it to DECtape.

So now we have BASIC, FOCAL, FORTRAN, and PAL languages on the PDP-8/I, all in just 4k of core.
Time to get some more demonstration programs!
 
You must log in or register to reply here.
Back
Top