Connecting a VT320 to a DECmate III?

[djfitzgerald]

I picked up a DECmate III at VCF East consignment, and tested it with David Gesswein's DECmate II monitor/keyboard. I don't have the monitor/keyboard myself, but I _do_ have a working VT330 that I use with my PiDP-11. Is there a disk image out there configured to let me use my VT330 as the sole interface when I boot the system? Or at least boot the system and immediately connect to whatever device is plugged into the serial port?

 

[DougIngraham]

If I am understanding you correctly then the answer is no. The DECmate computers are intended to talk to their internal video memory when a 604X IOT is seen and receive keyboard input from the attached keyboard when the 603X IOT instructions are encountered. It is not possible to make OS/8 or should I call it OS/278 substitute the serial port for the emulated console. I suppose it might be possible to modify the front panel code that runs in the 2nd 32k front panel code space and have it translate the 603X and 604X IOTs to talk to one of the serial ports but I have never looked that closely at the way the 6120 chip implements this stuff. I suspect it is not practical if it is possible. The DECmates don't actually emulate the console IOTs exactly correctly and you can write code that will work everywhere except for the DECmates. I suspect that if it was possible to have fixed this in software then it would have been corrected. Mr Lasner has a rant about it and I know that he reverse assembled the front panel code. It is something like the KSF will skip if a key is pressed but the KSF also clears the flag so you can only test it once. Not normally a problem but it is a change from the way all the other 8 machines work.

If OS/8 had implemented system calls to read/write characters to the console and all programs used these calls it would have been possible to make a small change to the OS in order to redirect the I/O to a different device. But OS/8 does not have such functions and every program that talks to the console talks directly to the hardware. In order to implement this you would need to recompile or reassemble every program you want to use.

The word processer software is not based on OS/8 and I have not seen any sources for it. I barely even ever used the WPS on a DECmate and I am not at all motivated to try to reverse engineer it.

The monitors and keyboards occasionally show up on Ebay. The monitors often have cataracts and the keyboards often have issues. I recall seeing some threads that talk about using modern replacements for the keyboard and monitor but I don't follow them so can't direct you to one of them.

I hope you find a way to use your DMIII!