27C512 EPROM in a C128

From: Niklas Ramsberg (niklas.ramsberg_at_swipnet.se)
Date: 2003-01-01 20:05:01

Hej allihopa!

I thought I should follow Nicolas Welte's instructions on how to replace
the 23128 ROMs in a flat C128 with 27C512 EPROMs. I really don't know
anything about how EPROMs work (more than how to program them that is).
Nicolas writes in the article:

> What are the advantages? I did it because I was in the process of
> changing the kernals of both the C128 and the C64 mode, and it is a
> big advantage if they're in one chip. I wanted to be able to switch
> between the original and the changed ones, so I used a 64k EPROM and
> put it into U32. I bent the pin with A15 out of the socket and
> connected a switch to it. Without the modification, I would've had to
> connect the switch to both EPROMs at U32 and U35.

OK, so I have to connect a switch to the pin that supplies A15 on the
27C512 (pin 1) to be able to switch in the upper 32K of the EPROM. I get
that. But where shall I connect the other pole of the switch?

/Niklas Ramsberg

P.S. Nicolas, I've bothered you enough the last few weeks, so I thought
I'd give you a break and let the other people on the list help me out

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