Re: Ultimax questions

From: Michał Pleban <>
Date: Sun, 20 Oct 2013 19:16:05 +0200
Message-ID: <>

Rob Clarke wrote:

> Have you tested that? I couldn't find any evidence that the decoding
> logic in the 6703 had ever been fully documented. It's possible that
> /EXRAM may be active up to $3FFF.

Yes, I checked that. Both in the MAX and in C64 in MAX mode there is
nothing above $1000. PEEKing values from 4096+ just return random stuff
(MAX) or zeroes (C64). The RAM that sits at /EXRAM is not mirrored up above.

> But even if it does, what then? I suspect even the MAX Basic ROM does
> not intelligently probe for usable memory and the extra 2k of RAM is
> hardcoded. So yes, we could probably fix the ROM to use the extra RAM

Of course :-)

> but I have no intention of typing in 32k BASIC programs on a MAX
> keyboard anytime soon. :-)

You could just load them form Datasette ;-) In fact, if given enough
RAM, then many BASIC programs from the C64 would work wuthout modification.


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Received on 2013-10-20 18:00:03

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