How to read recalcitrant floppies?

From: Jerome Fine <jhfine_at_idirect.com>
Date: Sat Apr 17 19:42:48 1999

aaaaa
>Ethan Dicks wrote:

> I am attempting to back up some floppies from a project I did a few years ago.
> The sets of 3.5" 1.44Mb IBM floppies have been stored in a box, in a cool and
> dry room. Out of one set of 12 and one set of 15 disks, I have four disks
> that have read errors that DOS won't get past, bad sectors and the like.

Jerome Fine replies:

You don't mention if the bad sectors are in the data or the file structure.
Also, if in the data, would a partial recovery of the file be acceptable?
Also, out of 2880 blocks for each 3.5" 1.44 MByte floppy, about
how many sectors (blocks) are bad?

While I can't help much with hardware recovery techniques, I can
guarantee that you can use RT-11 to at least write (copy) each diskette
onto a second copy with only the bad sectors not copied across.
If all the bad sectors are in the data files, you will at least recover
as much of the file as possible. Sometimes in RT-11, blocks that
are mostly bad can be encouraged to be duplicated by repeated
attempts. The copy utilities (PIP or DUP) have a switch to
repeat the read until it completely fails OR to IGNORE failures
and continue. I don't remember if a DEVICE copy has that
feature, but if you say you are willing to try RT-11, I can help
guide you through the process. What OS on what hardware
will you read the 3.5" floppy. If it is a PC under W95 (I use
it only to do e-mail - not by choice), there are very good tools
to help.

Sincerely yours,

Jerome Fine
RT-11/TSX-PLUS User/Addict
Received on Sat Apr 17 1999 - 19:42:48 BST