Apple /// stuff (was: Re: This weekend's haul)

From: Sam Ismail <dastar_at_crl.com>
Date: Wed Jun 25 11:52:25 1997

On Wed, 25 Jun 1997, Doug Spence wrote:

> I had just discovered, after several years of neglecting my ][+, that bit
> rot had set in on a fair number of disks and I wanted to put the data
> somewhere safe.

I've been really lucky in that respect. All my disks seem to be working
fine even after 10 years (tap on silicon). I still even have my first
two Dysan floppies that my friend gave me for my computer class in 9th
grade. Haven't booted them in a while though.

I know of a way to fix bad sectors on Apple // disks that requires a
little luck. I wrote a sector editor a long time ago that I used for all
my hacking. This editor allowed me to read and write sectors very
easily. I disabled the checksum verification in DOS so that when it came
upon a bad sector it wouldn't barf. It would just read whatever data it
found and then throw it up on the screen. I could tell if a sector
wasn't right by the look of its bytes in ASCII with relation to sectors
around it. I got very good at this. Whenever I found a bad sector on
one of my disks, I would run my sector editor, jump to the bad sector
then continually read it until I saw what I liked and then wrote it back
out. Worked like a charm. This would usually fix the problem, which was
caused by acute bit rot. This obviously won't work on disks that have
just plum gone bad, but I've had a phenomanol (shit can't spell today)
success rate.

If anyone wants to do this, you stick an $18 in $B942 (from the monitor
B942: 18) which disables the DOS sector checksum verification. Of course
you must use a sector editor which uses the DOS in memory.

Sam
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Computer Historian, Programmer, Musician, Philosopher, Athlete, Writer, Jackass
Received on Wed Jun 25 1997 - 11:52:25 BST