Re: SuperCPU for my C64 and C128

From: Mia Magnusson <>
Date: Mon, 23 Jul 2018 22:34:33 +0200
Message-ID: <>
Den Fri, 20 Jul 2018 11:30:20 +0100 skrev smf <>:
> On 20/07/2018 07:11, Baltissen, GJPAA (Ruud) wrote:
> > Are you sure that this happens with the SCPU as well?
> It doesn't, by default it mirrors writes to the first 64k
> This slows the super cpu down, because it can run software at 20mhz
> but if two writes happen one after the other then it has to wait for
> the first 1mhz write to complete.
> So you can turn off mirroring of certain ranges.
> If you add an ultimax mode then you still have to mirror ram at the 
> start of memory, but you have to solve the problem of interleaving
> the 1mhz vic reads into the 20mhz cpu reads.

The speed of the VIC-II reads won't be a problem, it's just a matter of
inserting one wait state for the 65816 unless you have super fast ram
that can run zero wait state at the equivalent of 40MHz, then you don't
even need a wait state. Such fast rams which might be available as cache
rams, remember that you only need 64k of those unless you want to add
register to let VIC access more than 64k.

> You still need to support all the supercpu mirroring schemes as well,
> or you won't be able to get the correct timing for demo effects.

Will 6510 based demos work at all on a 65816? I'd assume that they use
some well known illegal op codes?

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Received on 2018-07-23 23:00:05

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