Re: Technique to fix bad sectors??

[nathan@visi.com (Nathan Mates)]

In article <5n8rja$r9s$1@Jupiter.Mcs.Net>, Joe Walters <bird@MCS.COM> wrote:
>Today I tried to backup my Texas.II Vol 7 disk (REAL old history), and
>found that it had suffered bit rot (a Nathan Mates saying that amuses
>me and also describes the problem).

   I didn't come up with that name for it, but thanks.

>The disk now has six sectors on different tracks that are bad
>(1529 ($5F9), 1551 ($60f), 1564 ($61C), 1566 ($61E), 1581 ($62D),
>1594 ($634).

   Judging by these numbers, I'm assuming you have a 3.5" disk,
probably 800K formatted. Thus, COPYA probably won't work at all
(Rubywand, you better starting thinking before posting too) unless
the DOS 3.3 program is rewritten for smartport stuff, etc.

>My main hope became Copy ][ +. In the Sector Editor for 3.5" disks
>I can read the bad sectors if I use the Patched options to ignore
>errors in the checksum, etc. What I cannot figure out is how to tell
>Copy ][+ to write the sector out using computed checksums for the
>data.

   Here's my recommendation to fixing it w/ Copy ][+:

1. Bitcopy flakey disk to backup. This'll get a fair amount off.
2. For each bad sector, do the following:
  a) Turn off checksums, read from flakey disk
  b) Swap disks to good one
  c) Turn on checksums, write to backup disk

   I think that C2P's sector editor should be able to recreate the
sector somehow (I think I remmeber this working on 5.25" disks, but
not too sure). Otherwise, if you have the C][+ manual, there may be an
option to do something like this while copying.

   If this doesn't work overall, some work could be done in the sector
editor to excise these bad blocks from the file (at the loss of 512
bytes each, so you'd have to recreate more). That'd probably also
confuse AW a bit, so some form of content recovery might be needed.
Say something if you need this detailed further; I do not trust my
memory of disk internals while away from my GS...

Nathan Mates
--
<*> Nathan Mates http://www.visi.com/~nathan/      <*>
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# think-- what are the facts, and to how many decimal places?  -R.A. Heinlein