Tuesday, November 28, 2017

Still working to have two terminals active under RTE IV B


Working with RTE IV B

Editing files in the simulated RTE environment is quite a pain, due to the interspersed prompts of both system and file manager level that occur with a single terminal online. One of my latest attempts to produce a dual terminal system and activate both came to a bad end when I inadvertently set up the directory on the system disk cartridge so that it clipped part of the system code.

HP refers to partitions or sections of a disk cartridge as a cartridge, confusingly. My virtual 7920H disk cartridge, containing 411 cylinders each with 5 surfaces (tracks or heads), is divided into six portions. These are the system, GF, GN, HP, RT and SC (spare) cartridges.

Each cartridge has a directory and contains files. The system cartridge also stores the system itself, thus the directory for the system cartridge must begin above the end of the generated system. I mistakenly formatted the directory in a way that overlaid the tail end of the system. Back to step one!

At this point, I think I have built a usable disk image which supports my terminals and IO configuration. The image as used with the simh based simulator on a PC has its byte order swapped compared to the HP 1000, thus I need to run the dd utility against it to swap bytes back to their correct order for use with HPdrive.

I moved the image over to HPdrive and attempted to boot the image, but received a halt 102011 which means that the disk IO encountered an error. I switched back to the prior image I had been running and that too stopped with an error.

The one hardware change I made was to insert the second 12966A serial card in slot 23 in order to have both terminals active simultaneously. I had feared I had an error with the second card back a month or so ago, but it wasn't definitive. Time to pull various cards to test which causes the problems.

With just my original card in slot 22, the new system boots up fine. With just the suspect card in slot 22, the I/O error occurs during boot. The card is bad, perhaps driving an interrupt request or causing some other interference on the bus that blocks the higher priority disk controller card from succeeding in its I/O.

I still can't get the simulator to talk to more than one telnet session even with twin BACI cards generated and attached. I will see if I can switch one of the simulated cards from BACI (12966A) to an 8 port multiplexor, modify the WELCOM file to try to bring up a terminal on the mux and see if that works. This may be a defect in the simulator file, which might not support more than one BACI active at the same time.

I did download the QCTERM software from the HP Museum down in Australia. With it, I am no longer plagued by the dual prompts of system and file manager. The same happens on my physical terminals if I have auto-LF set but behaves fine with it off. Thus I can't use the built-in telnet client in Windows since it insists on CR-LF when hitting the Return key.

QCTERM won't run more than one copy on a system, thus I would have to go through some contortions to have two of these running talking to the HP simulator. I generated a system with a MUX card for the second terminal and continued to try to get the second terminal active under the simulator.

The telnet session did refer to connection to the MUX device, but that was as far as it went. My last test was to switch the telnet and QCTERM devices - using the telnet as the system console and attempting to use QCTERM as a second terminal. The results were the same - no signs of life from the secondary terminal.

Slightly frustrating - I just don't know whether there is something I am missing which is stopping the simulator image from running. I do know that I have a bad BACI card in real life so I can't try out dual terminals on the HP 1000 system. 

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