Re: How does the ZIP chip work?

["David Wilson" <mcs6502@gmail.com>]

Michael J. Mahon wrote:
 > The Apple II is a remarkably clever intertwining of constraints and
> capabilities that achieved unprecedented "bang for the buck" when it
> was designed.  Ironically, that very cleverness makes it much more
> difficult to just "speed up the clock" and still have an Apple II.

Indeed. My OSI Superboard II was a doddle to accelerate. The way it
handled the video chain and the CPU both needing access to the video
RAM was to give the CPU priority. Any time the CPU read from or wrote
to the screen, a short black line appeared.
Speeding up the processor had the advantage of reducing the length of
these black lines.
More amusing was to load a program into VRAM and run it - the video
display would be covered in black lines.