Re: Apple II emulator for GS/OS

[Rubywand <rubywand@swbell.net>]

> >Supertimer writes ...
> >>
> >> I'm wondering about the feasability of the title of this post.
> >> Since the IIGS has a 65C02 compatible processor, it
> >> would not be a full emulator, but you get the picture.
 ....

> >
> >     A challenge in running dsks under any emu on the GS is preventing damage
> >to hard disk, Zip disk, etc. files. Just running ProDOS dsks is no good
> because
> >most dsks are DOS 3.3, a speeded DOS 3.3, or some semi-deprotected weird DOS.
> >The required checking would take a chunk out of your speed.
> 
> I'm basically interested in a "DSK Launcher" for the IIGS and or
> IIe.  If you look at a dsk image in a file editor and compare it to
> a DOS 3.3 Launcer image, they are almost identical.  The difference
> appears to be the order the tracks/sectors are stored.  This is
> not surprising because DOS 3.3 Launcher images are identical
> to the images used by the II in a Mac emulator.  The catch is this
> emulator is no longer supported and pretty much forgotten.  It
> should be possible, however, to write a DOS 3.3 Launcher type
> program for the slightly different dsk format.
> 
> It is worthwhile to note that DOS 3.3 Launcher also supports the
> speeded up DOS 3.3s.

     DOS 3.3 Launcher or some Dsk driver is fine for some software. However, if
you want the simplicity which comes with being able to turn over the system to
6502 software running under 'old II' hardware in the GS, how do you guarantee that
dsk-based software will not crash or, even, bomb files on your hard disk?

     Intercepting standard DOS 3.3 and ProDOS commands is no problem. What do you
do about machine coded access to Slot 6 or to the 'current drive' Slot?

     The emu approach might work; but, it seems intuitively goofy to put up with
the loss of speed and complexities involved just to emulate an Apple II on an
Apple II. Besides, it would not be all that easy to guarantee that some piece of
code does not make an incorrect Slot access. (And, someone would need to write the
thing.)

     It looks like the only reasonably safe place to run a 5.25" dsk on a GS is on
RAM disk dedicated to Slot 6 via a hardware plug-in. Again, someone would need to
design and build something new; but, it would get the job done without a lot of
hassle and there is a good potential for sales and profit in having easy,
high-performance access to hundreds of dsks.

     Otherwise, you have the alternative of speeding up and streamlining the dsk
conversion process. For example, you could just leave a couple diskettes in your
5.25" drives and SuperDSK2FILE or AsimovX would take care of correct formatting
and moving 5.25" dsk files there whenever you wanted to play some game.




Rubywand