Re: 65816 and I/O
Date: 2001-01-20 01:32:33

My understanding of the SCPU is such that it starts from a
"game" rom.  This occured to me when I built my twin-PSU setup for my
c64/SCPU, which has a two-second delay between my c64 mainboard firing up
and my scpu getting power.  This isnt harmful, but it keeps anything on
the cart port from starting automatically until I hard-reset the c64.

The c64 came up fine, but with 8k less ram than normal, due to the
presence of the "game" rom in the scpu that does various unknown things
before starting the beast up.

Back to the topic,

Since the machine starts from a game rom, I/O will be mapped in.  Once the
SCPU gets permission to start, it locks DMA mode permanently, with I/O
enabled, and mirrors key locations to the c64 upon write, I.E. Dxxx, 0, 1.

The entire contents of RAM are also mirrored at an unknown (to
me) interval unless you select an optimisation mode, but that's beyond our
scope. ;)


On Fri, 19 Jan 2001, Ruud Baltissen wrote:

> Hallo allemaal,
> In my previous mail I also had the plan to ask you what the best way is to
> expand a C=. (that's what the subject "memory expansion" originaly was meant
> for). But personal circumstances forced me to stop writing so I sent it with
> the question.
> FUNET provides a way to expand, the memmory of a C64 or C128. The big
> problem is you won't find SW to support it. Looking from the SW side, you'll
> find three systems: 1) GEOS-RAM 2) the REU and 3) CMD.
> CMD is capable of expanding up to 16 MB. My first thought was to use the
> same trick until I realised that the trick was the fact they used the 65816.
> This is not exiting as I already made a design based on this principle. But
> it triggered a chain reaction: if they use the 65816, how about the I/O area
> of the 6510? There are, AFAIK, only two solutions:
> 1) the 65816 tells the 6510 in some way to perform the needed actions.
> 2) even if the 6510 is disabled, it is possible to adress the I/O area.
> I think it  is solution #2. Is this a known fact, or can this be checked?
> This would mean I can simplify my own design.
> And if it can be simplified, why not designing using the known specs of CMD.
> What kind of technical info of the Super-CPU is available?
> Thanks for any info.
> Groetjes, Ruud
> -
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