Re: C64 Proggy to read/write Apple II?

[supertimer@aol.com (Supertimer)]

Cameron Kaiser <cdkaiser@delete.these.four.words.concentric.net> wrote:

>Crossposts to comp.sys.apple2, who probably know more about this than I.

My AOL newreader is going to chop off the cscbm part of the cross
post so this reply is going to show up only on csa2, sorry.

>Uber <uber@wizvax.net> writes:
>
>>I remember products years ago... Mimic for the 64 I think, which
>>was hardware... But if the 1541 does GCR and stuff, you would
>>think that there would be no need for hardware addons if you
>>just want to swap files/disks/images...
>
>GCR isn't standardized between platforms. IIRC, the Apple's GCR encoding
>table is different from CBM's, and moreover, Commodore disks have different
>data density (angular velocity?) depending on the track's distance from the
>disk hub, a trick unique to Commodore because they patented it.

First, variable speed GCR is not unique to Commodore.  The Apple
800k GCR format uses it (old Macintosh and 800k Apple II 3.5 disks).

Second, the 64 product is Mimic Systems' Spartan, an Apple II+
hardware emulator for the C64.  Part of the package included a chip
that you swapped with one inside your 1541 drive.  This made the
1541 drive "Apple II" aware.

The catch is the drive (possibly) no longer reading C64 format.  ;-)

I'm not sure about this point 'cause I only got this impression
from reading Compute's Gazette review of the Spartan.  It said
that the mod made your "smart" 1541 drives "dumb" in order to
read Apple II disks.  I assume this means that it is a sort of
change that works only one way at a time.  I could be wrong
about the drive no longer reading C64 format.  Either way, the
mod DID allow the drive to read Apple II disks.