Re: 16K memory expansion for Vic-20

From: Ruud Baltissen (
Date: 2001-01-10 07:34:23

Hallo Per,

I can add at least one simplification to your design. RAM doesn't care what
addresspin is connected to which addressline. For example: if you swap A0
and A1 and write something to address $xxx1, it will end up in $xxx2 inside
the RAM. But reading from $xxx1 will read it from $xxx2 inside the RAM
again. With other words: the outside world doesn't see the difference.
The reason you cannot use this trick with ROMs (like replacing a 2364 with a
2764) is obvious: you cannot use ROMs programmed by people using the the
original pinouts.

The simplification is
1) connect RAM-pin 23 (A11) to ROM-pin 21 (A12)
2) connect RAM-pin 2 (A12) to ROM-pin 18 (A11)

Groetjes, Ruud

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