Run using SIMH

[larsbrinkhoff]

I promised to look into this.

There are some prerequisites to do first:

1. Finish the "NG display" pull request: PDP11: NG - Tom Knight vector display simh/simh#642
2. Build on 1 to provide inputs from USB joysticks.

When these are in place, it shouldn't be much work to add a new display device (by way of D/A), and a new A/D input device.

[larsbrinkhoff]

Step 1 was finished.

[MattisLind]

Great! My progress on getting the VR12 working hasn't been that great. Will resort to use a small Tektronix 603 instead.