Re: SuperCPU for my C64 and C128

From: Mia Magnusson <>
Date: Wed, 25 Jul 2018 00:56:13 +0200
Message-ID: <>
Den Tue, 24 Jul 2018 05:46:39 +0100 skrev smf <>:
> On 23/07/2018 23:48, Mia Magnusson wrote:
> > No, the VIC can only read, never write, so it's unidirectional. And
> > I'm assuming buses in sync.
> It's bidirectional. The VIC can read, the 65816 can read and write.

We are talking about VIC reading from fast ram here, aren't we? :O
> In the SuperCPU the 65816 decides when to run at 20mhz and when to
> slow down to 1mhz,

Well, it's true that you have a software selectable 1MHz mode, but the
memory hardware will itself slow down the CPU when the CPU accesses
1MHz address space (i.e. the first 4k if not using shadow, and all I/O).

> throwing in ultimax mode then you have to also pay attention to vic fetches.
> It needs to be optional, or you will kill timing with existing
> SuperCPU software.

What SuperCPU software are there that really uses exact timing?

But yeah, as VIC-II anyway will use C64's internal ram for the first
4k, all logic to handle not using my proposal is already there so it
would be super easy to add an on/off function.

> What you're describing sounds more like 

Haven't heard about that, but the wiki article lacks technical details.

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Received on 2018-07-25 01:02:36

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