Video card question

[plasmo]

You can decode the 38.4K region of graphic memory such that a data read in that region also write the data into the pixel shift register. This way a separate write operation is not needed. So the instructions are read, increment index, and repeat 80 times to display a line of 640 pixels. While waiting for next horizontal sync, the software can read the PS2 keyboard shift register, and output a byte of sound. So it is a standalone computer with video, keyboard, and sound.
Bill
Edit, the design is described here,
viewtopic.php?f=4&t=6517&hilit=Vga65

A demo toward the end showed mixed text and graphic with screen scrolling feature. The graphic is BadApple in 192x144 resolution playing at 17 frames/sec
download/file.php?id=20272&mode=view

[BigEd]

Yuri wrote:

dorgon wrote:

[Andy Toone's] VideoBeast. https://feertech.com/microbeast/videobeast.html

I wish I had known about this sooner. The page doesn't look like it has been updated sense last year though. Any idea what the status of this project is?

Andy Toone exhibited his projects at the recent RetroFest in Swindon - I had a good chat with him. He's certainly still active.

[jgharston]

Video RAM address counters and data fetch is a "solved problem" with old parts. I'd base everything around a 6845CRTC. Going for ZX80-style manual pixel wrangling is a special type of masochism.

[cbmeeks]

I haven't read every response but I thought I would throw my $0.02 in.

For my project, I plan on using the Pico9918. Which is a drop-in replacement for the TMS9918. However, it has some extra advantages. First, it's somewhat affordable (relatively speaking) at $35 before shipping. However, it seems it's out of stock at the moment.

https://www.tindie.com/products/visrealm/pico9918/

It's FOSS so there's nothing stopping you from having JLCPCB or some other company build it for you.

Other advantages are that it's 5V tolerant since it's a drop-in replacement for the TI-99/4a, Colecovision, etc. And, I believe Tony has implemented most, if not all, of the F18A's advanced features like scrolling, GPU, etc.

And since it's based on the RP2040, there's nothing stopping you from reprogramming to some other video card if you have the ability.