[Blindapple] copying Dos to non-talking disk

[Jayson Smith]

Hi,

Unfortunately, ProDOS stores the volume directory and the bitmap, 
showing which blocks are free and which are used, on track 0. So if the 
entirety of track 0 is bad, all that information is gone. Without the 
volume directory, there's no record of the volume name, main directory 
contents, etc. Also, I think block 7 contains user data, which probably 
means one file or directory if it's just one block long, or the first 
block of some larger file, or some random block of some random file if a 
lot of deleting and moving around has happened. If this is a bootable 
disk, it's likely, but by no means guaranteed, that block 7 has the 
first block of the Prodos system file, in which case, that's no great 
loss. I'm assuming this is a 5.25 disk. If it's a 3.5 disk or a hard 
drive volume, track 0 contains possibly many more blocks, and thus, lots 
more user data may be lost.

As for repair, Do not! copy track 17 from any disk to track 17 of the 
problem disk. On most if not all ProDOS disks, track 17 contains all 
user data, and no filesystem data, so you'd be overwriting some random 
blocks of one or more random files. copying a clean track 0 to that disk 
would make that disk look like the volume from which track 0 was copied. 
If you have something like Mr. Fixit, you might be able to then scan the 
disk to try to find folders if the data was organized into folders. If 
there are files in the main folder, you probably won't be able to 
recover them properly if at all, since info about their names, types, 
sizes, locations, etc. is probably lost.

I'd suggest imaging what you can of the disk, or making a copy, maybe 
with Copy II Plus or similar which can do raw nibble copying, so you at 
least have a backup of what's still there, in case your repair efforts 
make things worse.
Jayson

On 4/30/2014 10:13 PM, Tom Brennan wrote:
> I've a problem.  I know the original thread of this topic is a month old but
> I've not had internet access for awhile.
>
> I've a prodos disk with a bad track 0 on it.  If I use a track copy program to
> replace the track with a clean track 0 from another prodos data disk is there
> any way that I can get back my vtoc information other than byte reading the
> disk?
>
> Tom
>
>
> Tom Brennan  KD5VIJ, CCC-A/SLP
> web page http://titan.sfasu.edu/~g_brennantg/sonicpage.html
>
>
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