[SiriusHardware]

One thing I have noticed which never occurred to me before is that the falling figure's head is somewhat stretched (in height) compared to the head of the 'landed' figure - not your fault, that's presumably just how the figure was originally defined. I've just never noticed that before.

It's interesting that the access clash from both sides at once seems to cause occasional corruption, how are the left and right sides prioritised, does one side always win or does accessing from the left temporarily lock the right side out, and vice-versa?

I'm surprised you are not using a read signal line (output from Pi, input to dual port RAM) and actually I was going to ask if you have also implemented write ability from the Pi to the Dual-Port RAM because if you do that you then have something quite powerful and independent of the VDU feature, the possibility for the Pi to send executable code directly to the dual-port RAM.

For example, I presume that replacing your original RAM/ROM expansion with this project means you've lost the facility of your fast-loader code which was held in 512 bytes of EPROM at 0200->

If you give the Pi the ability to write to the dual port RAM as well as reading from it that opens up the possibility of having executable code stored in an array in a Pi script which can then fast-load it into dual-port RAM, so for example you could have your VDU script run a one-shot startup procedure which pre-loads your tape fast load code into dual port RAM at 0200-> ready to be called whenever you want to load something quickly from the ESP32 loader - but - further than that, you could store full sized MK14 programs as data arrays in Python scripts and fast-load entire programs from the Pi into dual port RAM, the only limitation being that some of the original programs from the manual may need to be rewritten to run at addresses in the dual port RAM area if they are not already fully relocatable.

As regards the difficulty of connecting the SOC VDU to a modern display, I only very occasionally connect mine to a contemporary black and white UHF TV. Usually, I just make clip lead connections to the composite-video input of the modulator and jump that signal across to the composite-in of my Philips CM8254 video monitor, from the 16-bit (Atari ST / Amiga) era and it works fine. I think Tim said he does something similar. Very likely, the sort of conversion where the innards of the modulator are removed and replaced with a composite video buffer, commonly done on ZX81s, would work on the SOC VDU but I could never bring myself to modify mine so heavily now, not when it has survived for so long in its original form.

However, fast forward to today and many TVs aren't even coming with composite AV or SCART inputs any more and the only kind of input you are guaranteed to find on a modern TV is HDMI, so your project is 'just in time'.