From: Richard Atkinson (
Date: 2000-09-27 05:43:03


Very interesting project. I and several others talked about VIC-II
reverse-engineering projects for several months and it comes up quite
frequently on csc in the form of the "someone should do a c64 on a chip"
thread. However, it was only in the past few weeks that I actually started
on my VIC-II in Verilog project in earnest. My new job at had something to do with it... It's not really got to
anything like the stage yours has, of course.

Anyway, I'm interested in adding VIC-II compatibility to your design, but
some fundamental decisions have to be made. Originally I proposed an FPGA
with some pins that were plug-in replacements for the real VIC, but made
no attempt to provide an analogue interface (of course). Instead, a 4 bit
(or possibly 8 bit) digital output for the colour numbers at the current
pixel (the extra 4 bits being for the line above which is relevant in a
PAL emulation) was the plan. Then I thought about integrating a "RAMDAC"
too, with some method of changing the default colour allocations in case
the user didn't like them.

What's your ultimate aim for your video chip project? Will it be a plug-in
replacement for the VIC-II or a hybrid similar to mine or a second display
like the one in the SID socket at the Expo? Leaving aside C64-on-a-chip
concerns for now, I think the VIC-II is the first hurdle. PAL/NTSC and
revision selection are easy enough to implement, hence I included them in
my original spec. What I left open (although thinking about them for a
while) were enhancements to the VIC-II; particularly a second memory
interface for high speed video accesses (hires video modes etc) and the
precise details of how the analogue video interface would work. I
certainly had connection to an RGB 15kHz television-style monitor in mind,
though. VGA was not in my original plan.


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