Hi! Thanks Dave! It never hurts to have another video board! Most likely we’ll standardize on the S-100 VGA board once it is done but that may be a while. The S-100 uPD7220 GDC board will be able to use standard VGA monitors (CRT and LCD) since it uses regular dot-clocks. The S-100 VDP has VGA compatible signals but still retains the NTSC dot-clock which makes monitor compatibility kind of tricky. Really the only good options for the S-100 VDP VGA output are really old NEC multi-sync CRT monitors or the newer LCD monitors which share common circuitry with a TV counterpart model.
The NEC uPD7220 GDC is an interesting historical chip in its own right. I consider it part of those many alternative history discussions like what if IBM has chosen CP/M 86 instead of MS-DOS, used a 68K instead of 8088, used VME instead of ISA, etc. The NEC uPD7220 was generations ahead of the MC6845 (essentially a glorified address generator) and we’ve been straddled with the latter for thirty years. It took another 10-15 or so years for accelerated graphics primitives to enter in to the mainstream of PC architecture due to the backwards nature of the MC6845. What a kludge!
Unfortunately the uPD7220 lacks a BITBLT function however I am sure that had it become popular that function would have appeared soon. Pair the uPD7220 with a DMA chip and you get the same effect. Basically just slinging huge hunks of bits around memory address space at break-neck speed.
At least in theory, it would be possible to write an X-server for the uPD7220 but I imagine the performance would be terrible. For that matter, it would also work for the upcoming S-100 VDP but would have similar results. Still it is good to have options.
The S-100 uPD7220 as envisioned is an IO only device. It doesn’t have to be like that but it is how it was implemented on the N8VEM ECB system so I just ported it. I could alternatively be a memory board (shared between the uPD7220 and system memory) as well but would require a significant redesign.
Thanks and have a nice day!