Re: Eagle CAD design and fabrication of C64 & Plus4 cartridges

From: bwack <>
Date: Sat, 3 Jun 2017 09:15:34 -0700 (PDT)
Message-ID: <>
Hi Jim and Mark. I became one of the testers. I accepted to receive and make
a video about it. I didn't know about this discussion at the time, and that
it was a quick mash-up, so this turned more into a pcb 1.0 review than an
easy of use review.

I've learned that the cartridge sets #EXROM or #GAME, and in some cases both
(16k). Then, why is there a double throw jumper for #EXROM and #GAME? I had
to bodge a link to tie the signals to ground. A jumper would just connect
one of them to ground. For a 2764 rom that would have been ok I think, but
not for 27C128 used for 16k game roms. Wizard of Wor cart (16k) is the
passion for this project.

I dumped the .crt file using cartconv.exe, using -t bin option and burned
the 16k with minipro. No problems there. So now the A13 on the 27C128 banks
the two 8k ROM areas.

One chipselect/outputenable, two chipselect signals:
Now the second thing I gather is that the PLA drives #CS and or #OE with
#ROML or #ROMH. Those signals are dependent on #EXROM and #GAME. Because the
overview doc I got from Mindflare says : "Single EPROM support - 2764 or
27C64 (1 x 8k bank) / 27128 or 27C128 (2 x 8k banks)", I decided to buy an
27C128. Here is the problem: a double throw jumper has no place on selecting
#ROML and #ROMH for #OE. It's either #ROML or both, right? The second
problem: I have a single chip, but two chipselect/output enable drivers
#ROMH and #ROML. Someone in the thread suggested two diodes and a resistor.
This was not everything needed to make it work. The #ROML was also connected
to A13, the MSB of 27c128's address bus.

It turned into a bodge job where non of the components (diodes and resistors
and links) has a place to go on the board other than into the air and then
back again. Just saying. Anyway not criticising here. I know (now) that it
was a 15min job. I did get Wizard of Wor to run today. Yay !

Hans / Bwack

View this message in context:
Sent from the cbm-hackers mailing list archive at

       Message was sent through the cbm-hackers mailing list
Received on 2017-06-03 17:00:05

Archive generated by hypermail 2.2.0.