Contemplating Graphics

I’ve been thinking about graphics the last week or two. One of the items on my list of things to do is to build a video board for the G80-S. However, graphics pose a new problem…

Video Processors of the time period that this computer would exist were very primitive in respect to their capabilities. Wanting to have a machine similar in capabilities to an MSX, this requires me to use a chip compatible with the TMS9918A. The problem with this chip is that it doesn’t have the greatest of text modes. 40×25 characters just doesn’t work for the Monitor program, or any future aspirations of CP/M or DOS, which typically require 80×24 or 80×25 text modes.

There is a solution to this. Grant Searle’s adaptation of Daryl Rictor’s AVR video processor to 80-column text Mode is perfect for CP/M or DOS. But the problem is that: 1) It’s not compatible with the TMs9918A graphics, 2) the graphics mode leaves quite a bit to be desired.

That leaves me contemplating what should be done. I’ve got some ideas, but I figured in the mean time I would play around with a few different projects, at least until my new boards come…

One of the things that I’ve been wanting to play with was a 128*64 pixel graphics display. I bought one off of eBay a while back, and I’ve never toyed with it. 128*64 pixels isn’t a lot to work with. But I figured I should at least be able to get the G80-S to utilize it for it’s display…at least for TinyBASIC. I’d like to have 32-columns at the minimum. At 8-rows that should give a decent display. But cramming 32 characters in a 128 pixel wide display is a chore.

But with luck I came up with what I though would be a decent character set. I’ve attached the images below for your critique. The characters are 4×8 (width x height). That should allow for a 32×8 display and still permit normal graphics. Now I just have to write some code to test it.




2 Replies to “Contemplating Graphics”

    1. “Your project interests me I am thought! Maybe there is something to do the VDP of the sega master system?” -translation.

      I think what you’re asking is if I pland to use the VDP of the Sega Master System. No, I plan to use the VDP of the TI-99/4A. Although my understanding is that they are very similar, and the VDP from the Sega Master System is derived from the TMS9918, they are in fact different VDPs. However, there may be a high level of compatibility. It’ll be interesting to see.

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