Dual-ported RAM is one oldschool solution. Usually it has a parallel (8 bit, for example) port on one side, and a serial port on the other. The CPU can address and alter bits/bytes randomly from the parallel side, while the RAM is also outputting an appropriately clocked serial stream to the video circuitry on the serial side.
But I get the impression that you are planning to have a single RAM space and a single type of RAM on the board?
BTW, direct video generation from micros is totally possible. Even a lowly PIC-18. Admittedly, that's still more powerful than a 128k Mac.
You might also investigate the Parallax Propeller, which has timers and whatnot, and prebuilt libraries, set up to do PAL, NTSC and VGA at thousands of colours. There are various projects around which use it as a sort of multipurpose I/O buffer to another CPU/micro.
Regarding the original Macs, it's worth remembering that they were one bit per pixel
Potentially useful threads:
viewtopic.php?f=7&t=11040
But I get the impression that you are planning to have a single RAM space and a single type of RAM on the board?
BTW, direct video generation from micros is totally possible. Even a lowly PIC-18. Admittedly, that's still more powerful than a 128k Mac.
You might also investigate the Parallax Propeller, which has timers and whatnot, and prebuilt libraries, set up to do PAL, NTSC and VGA at thousands of colours. There are various projects around which use it as a sort of multipurpose I/O buffer to another CPU/micro.
Regarding the original Macs, it's worth remembering that they were one bit per pixel
Potentially useful threads:
viewtopic.php?f=7&t=11040