Date   : Tue, 20 Jul 2010 17:30:51 +0200
From   : rick@... (Rick Murray)
Subject: ADFS Broken Chain - BBC Model B

On 20/07/2010 12:49, Rob wrote:

> Hopefully that should get you access to the directory, in which
> case, backup everything immediately - do not treat the disc as safe
 > to write to.

...and be aware that one or more files may be corrupt.


For that reason, Rob's advice:
 > Then format up a new CF card and restore everything
                    ^^^
is very good - keep the original (even if 'borked') until you are 
certain you have everything.

I suffered a screwed up root directory on one of my ADFS E floppies many 
moons ago. LookSystems disc recovery didn't want to know, and DiscKnight 
didn't exist. *CheckMap is pretty useless really, and *Defect is of 
limited use.

Needless to say it contained important documents. Backup? Backups were 
not pleasant on a single-floppy machine.

I didn't have the PRMs describing the disc layout (I do now and *still* 
don't understand it all!).

In the end, I cobbled together a BASIC program to OS_GPBP the entire 
disc into memory, so I could then clip out bits of files. It took a fair 
amount of work in !Edit to extract control codes and the like from 
Ovation files, and then (later) rebuild the file in Ovation. But... for 
all the aggravation [*], it was better than saying "oh well".

So, ALWAYS keep the original (even if damaged) until you know you 
absolutely no longer need it.



Best wishes,

Rick.

* - TBH I kinda miss those days. Who in their right mind would attempt
     such a thing on an NTFS partition? To that end, is there a disc
     sector editor that runs in DOS that even understands NTFS? Hell, the
     ones I have are *useless* with Flash media (USB, SD...) because
     those things use FAT32.
     I recall undeleting a file on FAT was dead easy as the FS simply
     corrupted the first byte and marked the dir entry as "available".
     Given XP does no Recycle bin ops on removable media, and how easy it
     is to "oops" delete the wrong file (or too many), it would be nice
     to poke the directory manually. I've tried literally dozens of file
     recovery programs. They're all slow, and not a single one, not a
     *one* has managed to recover an MPEG4 video file in such a way that
     anything will recognise it as video. Hex-reading the header, it is
     no surprise, it's just junk. Thank goodness 80% of stuff on TV is
     repeated, so if I delete the wrong file, set the PVR wrongly (it
     uses American mm/dd/yyyy dates so you can imagine the mistake
     potential), satellite on wrong channel, programme deferred due to
     f*ing world cup extra time... I can just sulk for a few minutes,
     then remember to keep an eye open for the next showing. ;-)

-- 
Rick Murray, eeePC901 & ADSL WiFI'd into it, all ETLAs!
BBC B: DNFS, 2 x 5.25" floppies, EPROM prog, Acorn TTX
E01S FileStore, A3000/A5000/RiscPC/various PCs/blahblah...