Wednesday, November 22, 2017

Still diagnosing why my 2621A terminal is not communicating with HP 1000 system


Working with RTE IV B

I did a number of system generations and initialized each, just to further build up my understanding of the RTE IV B world. I continue to be plagued by the simulator. What I want is to have two 12966A (BACI or serial cards) installed, with twin telnet sessions connected to them, allowing me to have a system console plus a regular user terminal.

Any attempt to boot up even in reconfiguration mode with BACI0 and BACI1 configured just hangs. I notice that when I set up telnet sessions, the connection occurs on BACI1 rather than BACI0, the reverse of the order I would expect.

With things swapped backwards - the first set BACI command actually sets up BACI1 while the second such command establishes BACI0 - I can get the system to boot up and talk to me on the system console. I still can't get the second terminal active.

I put that problem aside and worked on my system generation experiments - learning various utilities and trying things. The ultimate end is to have the best version of RTE IV B set up that I can, using the simulator, before hauling it over to the HPdrive virtual disk drive and running on the real system.

Once that is proven to work well, I want a version that can support the physical 7906 disk drive in addition to my virtual 7920H drive, allowing me to end up with a system placed on a fresh cartridge on the real drive. Of course, I would need to finish the restoration and alignment of the drive before I was ready to install RTE on the cartridge.

2621A terminal debugging

My first test involved swapping the 2622D terminal body and seeing whether the first messages from the tape diagnostic program show up on the screen. If so, it points at my 2621A terminal as faulty or misconfigured.

The good news is that something about the default configuration and cable is the fault, not the terminal hardware itself. The swapped terminal displayed nothing, just as the 2621A failed to show anything.

Before I set up for scoping or logic analyzers, I did some verifications. First, I checked that each signal line from the Centronics 50 connector is tied to the proper edge connector pin that will fit on the 12966A serial card in the processor. Then, I dug out the schematics and verified the signals on the terminal were the Centronics pins I expected.

I found some anomalies. The manual for the 12966A serial board has a cabling chart for the 2621A terminal that lists only a few pins on the Centronics connector, but the 2622 service manual shows a number of pins that are shown as shorted together. I have to take my time and reconcile these to understand what my wiring needs to be. Plus, I will cross check them to the schematics in the 13220 processor module manual for the 2621/2622 terminal

IBM 1401 Restoration work at CHM

We had one 026 keypunch that began making a squealing sound as it idled. After some disassembly, Frank found a pulley bearing that was making the noise. A touch of machine oil on the bearings and everything quieted up just fine.

Another team, Mike Albaugh and Marc Verdiell, continued working with the tape emulator on the quest to get the 1401 Fortran Compiler operational. Once they sort out those issues, we think we can get a FARGO and a COBOL system up, although the typical COBOL process is thought to be 30-60 minutes long, first producing Autocoder as an intermediate text before yielding the final executable. 

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