The bit rate for 1970's "game-quality" video still ranges between 5 and 10 MHz. If you intend to do that in firmware, you've got to be moving along at a pretty good rate.

The old PONG game used a solid block of a fixed height and width as its primary moveable object. This was still generated with a character generator and shift register, and the circuitry that produced it operated at a fixed rate with which the CPU had to be synchronized. Only one movement per frame was allowed, since it would otherwise not have been easily visible.

The PONG games I remember didn't interlace the display as broadcast TV does. I think, typically, they used something on the order of 6 MHz as a dot-clock.

An 805x would have a bit of trouble both synchronizing with the display unless it limited itself to writing to the display memory during horizontal blanking, in that the display would be "hashed" each time the MCU collided with the display hardware's access to the refresh RAM. You could, I suppose, attempt to accomplish the dot-generation by using the serial port in mode-0, if you have a one-clocker.

BTW, live-broadcast TV is at the LOW end of performance and resolution. What's more, it's interlaced. If you've sat in front of one of the old terminals that used 30Hz interlace as the NTSC standard does, for more than 2 minutes, you know how annoying that is when you're trying to read characters or track small icons as they move about.

RE