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68766 8k eprom in the 600 Rev D

Posted: Sun Jun 16, 2019 1:37 pm
by waltermixxx
Success, last night Josh and I put the finishing touches on his 600D.
We did the 9600 baud mod, fixed the colour ram issue, brought TX out to pin 2 on J3,
And just for fun, we setup the 8k uk101 68766 eprom in U9, and cut/jumpered the board to us it. So now all 4 eprom sockets are selectable (bank selectable?) depending on what you put in the 55296 “register”. It controls BK0 and BK1.

Rom socket defaults to U9.

I modded my board to follow suit. I will help Steve’s with his, so he can, yet again rewrite his SJGMON initial menu to select which rom you want to start with. (That’s the theory, anyway.).

So a fun OSI 600 night for sure.

Two small cuts on the solder side of the board to isolate he 74LS138 A and B inputs from the rest of the OSI.
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Address AII and Adress A12 need to be hooked up to the eprom, pins 18 and 21,
and disconnected from +5 and Gnd. Cut the jumpers and connect to the address lines.
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BK0 and BK1 need to be hooked up to the LS138 A and B input to select which eprom.
6EC4DDB6-4CD6-48D5-A431-B78C9C159DAB.jpeg
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Re: 68766 8k eprom in the 600 Rev D

Posted: Sun Jun 16, 2019 2:12 pm
by Steve Gray
Very nice!

At some point could you write up a little text file detailing the mods?

Steve

Re: 68766 8k eprom in the 600 Rev D

Posted: Sun Jun 16, 2019 3:27 pm
by waltermixxx
Yup it was my intention to do just that, as soon as I had a chance.
I would most likely edit the first post with the details, seeing as the pics are already there. :)

:)