Re: [stella] Emulating the SC

Subject: Re: [stella] Emulating the SC
From: "Eckhard Stolberg" <Eckhard_Stolberg@xxxxxx>
Date: Wed, 9 May 2001 15:00:41 +0200
> Out of curiosity (and please forgive my laziness), what emulators fully
> support the SC?  That is, allow you to write to all the RAM addresses the
> supports, invoke multiloads, etc?  Essentially the SC is one giant stick
> RAM once you get a load in, right?  Every address is up for grabs?

None of the current VCS emulators supports the SC, as none of them
really emulates the loading mechanism or even provides the original
loading ROM. The emulators only trap the entry points for the loading
routine and then swap the data automatically. So on a real SC you
could probably write a loading routine with a game specific display,
if you really wanted to.

For all the other stuff PCAE, Stella and z26 do a pretty good job,
but of course I think z26 is the best of the three. ;-) At least
it allows you to get taunted by the Mindmaster, when you lose all your
lives too quickly. ;-)

If writing is enabled, you can write to any address of the 6K SC-RAM,
but you can access only two of the three 2K banks at a time. And for
the bank that is mapped in at $F800-$FFFF, you can't write to adresses
$FFF8 and $FFF9, as they are used for the SC control byte and the
audio interface. Turning of the writing ability can be usefull, if you
want to execute some code in $F0xx, as this area is used for invoking
the write mechanism.

And as Glenn has pointed out, you can reload any part of the 6K RAM
in steps of 256 bytes. But the loading routine uses the last 256 bytes
of the first 2K bank for the starfield display. Therefore you always
have to reload this area, if you want to use it in your own game.

Ciao, Eckhard Stolberg

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