Re: Uploading to Asimov

[Andy McFadden <fadden@fadden.com>]

In comp.sys.apple2 Ed Eastman <noone@nowhere.net> wrote:
> Either 5.25 inch (140k) disk image, DO or PO, can use the DSK extension, 
> but normally they are DO images.  I think emulators look at the first 
> 256 bytes and if it's prodos, assume PO and assume DO for everything 
> else when they encounter a DSK.

Generally speaking, ".dsk" is assumed to be ".do" for 5.25" disks
and ".po" for 3.5" disks.  You can't just look for DOS vs. ProDOS on the
disk, because a DOS disk could be in ProDOS order, and a ProDOS disk could
be in DOS order.

5.25" disks have 16 sectors.  If a DOS application was used to create
the image (e.g. ADT), it stored track 0 sector 0, then t0s1, and so on.
If a ProDOS application was used, it grabbed t0s0, then t0s2, because
"block 0" uses sectors 0 and 2 rather than 0 and 1.  It jumps around
like this for the rest of the track.

To figure out how the disk is stored, you have to guess what's on the
disk and then try reading sectors in different orders until you figure
out what's there.  Of course, if it's not a 5.25" disk, it probably
doesn't have 16 sectors and ".do" doesn't make any sense.

> Of course I'd like to see a 400k DO image supported so I can make really 
> big virtual Dos 3.3 diskettes. :)  (Hello Oliver/AppleWin developers, 
> Andy/ Ciderpress)

CiderPress supports DOS 3.3 images in a variety of sizes.

Hold down the "shift" key while you select File->New->Disk Image.  Now,
when you select "DOS 3.3", you can put a value into the "specify size" box.
Put in 800 blocks for a 400K disk image.

This isn't an officially supported feature.  Some values may not work or
will do strange things.  128K and 400K have been tested and should work.
It creates 400K disks in ".po" order because they don't have 16 sectors.
(It also creates 128K disks in ".po" order because it's not smart enough
to do it the other way.)

You can also use the Volume Copier to copy 400K pieces on and off of
Uni-DOS/AmDOS/OzDOS disk images (which have two 400K volumes on an
800K disk).  This isn't all that useful, since CiderPress can access
the volumes in place, but it's sort of fun to play with.

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