View Single Post
Old 31st Jan 2021, 8:57 pm   #420
Slothie
Octode
 
Join Date: Apr 2018
Location: Newbury, Berkshire, UK.
Posts: 1,287
Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by Mark1960 View Post
Does the video circuit of the pet drive the buffered address bus, or is there a separate interface to video ram?
The counter chain that generates the address for the video RAM and the CPU address are fed into a multiplexer that goes to the video RAM ony. There is no way for the current video ram address to get onto the cpu address bus as the video RAM is completely seperate from the system RAM, the CPU just sees a "window" at $8000 to access it.
Slothie is offline