Re: Switchless ROMs

From: Michał Pleban <>
Date: Mon, 26 Dec 2016 23:51:25 +0100
Message-ID: <>

smf wrote:

> Another method you can use is magic read sequences. i.e. come up with a
> sequence of rom reads that wouldn't happen in normal circumstances, long
> enough to make accidental activation so unlikely that it's practically
> impossible for there to be a collision. Then have the next read after
> this sequence use the address bits as data lines for writing the new bank.

In this scenario, you don't have the RESET line, so once you select a
KERNAL, you are stuck with it until the computer is switched off. Unless
you can somehow detect the actual reset sequence of the 6510 just by
looking at KERNAL accesses, but I am not sure if it is ever possible.

If you accept this limitation, then you actually don't need any magic
sequence at all. You just boot into the menu, the user selects the
KERNAL from the menu, then a single read from e.g. $E0xx selects the
KERNAL and disables further selections.


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Received on 2016-12-26 23:00:02

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