Serial USB Port / simh Script File Location?

[Casey Bralla]

I want to make the PiDP8 experience as close to the original as
possible.  I've throttled the CPU so the system runs at normal speeds,
but I also want to reduce the terminal speed to simulate an old Teletype.

I want the terminal to run at 110 Baud, just like the good old days.

My thought is to use a couple of USB-to-serial converters and log in via
serial.  The docs at
https://tangentsoft.com/pidp8i/wiki?name=Serial+or+Telnet+PDP-8+Console
describe how the simh language scripting can include a separate serial
console.  They quote the line "set console
serial=/dev/ttyUSB0;1200-7e1", but don't explain where (which file) to
put this statement.

Where is the simh command language script that pidp8 executes?

TIA!

Casey

[Randy James]

We ran VT-52’s at 4800 and one ASR-35 at 110. The 8/e couldn’t reliably drive the VTs at 9600 even though the interfaces had a 9600 setting.

> On Dec 24, 2024, at 2:19 PM, Casey Bralla <casey...@gmail.com> wrote:
>
> I want to make the PiDP8 experience as close to the original as possible. I've throttled the CPU so the system runs at normal speeds, but I also want to reduce the terminal speed to simulate an old Teletype.

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[Steve Tockey]

Casey,

The boot files for the PiDP-8/I are in the RasPi OS directory:

/opt/pidp8i/share/boot

The files are named 0.script, 1.script, 2.script, ... where the digit in the file name corresponds to the IF switch configuration when you trigger the boot into that particular configuration. I will assume for now that you are booting into normal OS/8 where the IF switch configuration is octal 0 (binary 000). The corresponding file would be /opt/pidp8i/share/boot/0.script. You can open that file using the RaspPi OS text editor (which is very straightforward) and just add that command.

If, as an example, you want to boot into a configuration using IF switches set to 6 octal (binary 110) then the proper boot file would be /opt/pidp8i/share/boot/6.script.

You also have the option of first experimenting without editing the boot script file. Simply boot into the unmodified configuration you want to experiment with. While that configuration is running, type Control/E on the console terminal. This will drop you into SIMH. Just directly type that "set console ..." command to the simh prompt. Then type "g" or "go" to the next simh prompt to restart the simulator. If there is some problem, you can Control/E back into simh and try a different command. Once you're sure you have the command you want, then you can edit that command into the appropriate /opt/pidp8i/share/boot/*.script file. From then on, that command will be executed every time you boot into that configuration.

Cheers,

-- steve

[Warren Young]

Beware that a good many USB to serial adapters have speed floors above what PDP-8 era equipment could manage. 110 bps to emulate a Teletype is likely to be right out, and even 300 bps for the “high speed” paper tape reader might not be allowed. 

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