Re: Switchless ROMs

From: Michał Pleban <>
Date: Thu, 29 Dec 2016 19:28:40 +0100
Message-ID: <>
Hello! wrote:

> If we want to keep compatibility - I am afraid the answer is "yes". A simple example: a program uses the RAM area under KERNAL as a temporary storage and reads from the consecutive addresses there. I know for a fact that such programs exist. So you would need to monitor the configuration bits or the _CS or ... The next example is copying KERNAL from ROM to RAM - lots of programs to this in order to modify a few things in the KERNAL. Here monitoring the _CS won't help as the program reads from ROM locations and you know what happens when you don't differentiate between the _RST induced reads and the same done by the program.

This is a valid point. As Gerrit said, you cannot distinguish the CPU
reading the reset vector during the RESET, and the CPU reading the reset
vector as a part of some user code.

So it looks like the only thing you can do is to hook some more control
signals from SID or VIC.


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Received on 2016-12-29 19:00:35

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