Microprocessor Board Plans for Old School CPUs: 6502, Z80, 6809, etc.

I had intended to use it to learn x86 assembly, and I did, but due to who I am as a person I got distracted by another project and moved on. I did learn some assembly and I think a skilled person could make any of these boards do useful work, though probably not very power-efficient work.

But at the same time, they're (mostly) representative of the bulk of the 8-bit scene. They only go so far.

Ben Eater demonstrates what it takes to get a 6502 up on a breadboard (and, with the modern processors and RAM, it's not a whole lot).

In the Z80 world, there's dozens of little Z80 systems with a UART and a flash drive booting CP/M in all sorts of form factors.

But that's where it stops.

There isn't anyone going full boat with a comparable 8-bit video system. The primary question of folks looking at these things, or wanting to do one themselves, is "how do I do video". They all want memory mapped video. Many want color and sprites.

But even skipping color, something akin to a TRS-80 and it's 64x16 screen on a hacked TV set. Or the PET or Apple 40x24 B&W characters. Forget graphics and color and lines. How about "hello world"? I mean, Woz did it with paperclips and shiny gum wrappers, at least so I'm told.

That's where things go off the deep end. It's like there's these simple baby steps to get to a UART, but video? That's...just not in the cards.

Ben Eater did a nice series on getting a VGA video signal using discrete components. It's really informative.

Demonstrably video is very difficult. Apparently anyone that can decipher a tool like KiCad can come up with a 8-Bit processor and a UART. But nobody, anywhere, is doing video.

The few that are doing anything are these retro clones striving to duplicate C-64s, trying to step above the hobby market and break out with a commercial product. But even they struggle.

I just find it curious how this last step seems so out of reach.

The problem may simply be there's nothing to display video on. An 8-bit machine driving even a VGA monitor is asking an awful lot, and I don't know what it takes to convert composite video to run on a modern display, either a VGA or HDMI. I would think if someone came up with THAT circuit, composite in, VGA out, as a "black box", something the board designers could plug in to, like the old RCA boxes we used to use tuned to Channel 3, then maybe that's the breakthrough thats missing from the community. They they could fall back on the old composite circuits from that past.