Date: Thu, 10 May 2001 14:00:00 -0600 (MDT) From: <janb@cs.utep.edu> To: "Julian Stacey Jhs@jhs.muc.de" <jhs@jhs.muc.de> Cc: "Brian W. Buchanan" <brian@CSUA.Berkeley.EDU>, J Wunsch <j@uriah.heep.sax.de>, <hackers@FreeBSD.ORG> Subject: Re: fd driver hacking to recover data Message-ID: <Pine.GSO.4.30.0105101358260.27302-100000@gecko> In-Reply-To: <200105101651.f4AGpMh58396@jhs.muc.de>
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I wrote such a program on Win2000. If you feel this is helpful,email me and I will send it to you. JAn > > I have a program that will rescue your data ! > It runs on DOS-3.2 & FreeBSD-any BUT the rescue component only runs on DOS > (however at least you can compile & play with it on BSD to get used to it). > > I have no idea if the FreeBSD ports DOS emulators allow access to floppy > hardware or not ? If not, the other options are: > - to boot with DOS to run my program, > - or modify the FreeBSD fd driver to pass the buffer on error. > > By chance my program was just being discussed on another list, Here's extracts: > --------------------- > > Message-Id: <200105072157.f47LvVs42257@jhs.muc.de> > > To: freebsd-scsi@FreeBSD.ORG > > Cc: pechter@ureach.com, "Ron Klinkien" <rklinkien@chello.nl> > > Subject: Re: Recovered data with positive head offset field replaceable unit msg > > Date: Mon, 07 May 2001 23:57:31 +0200 > > From: "Julian Stacey Jhs@jhs.muc.de" <jhs@jhs.muc.de> > > Sender: owner-freebsd-scsi@FreeBSD.ORG > > > > <stuff deleted> > > > > It's possible to recover most text data from bad floppies by repeat > > scanning, even without varying the offset, even with failing CRCs: > > I wrote a program that does that in ~87 > > http://bim.bsn.com/~jhs/src/bsd/jhs/bin/public/valid/valid.c & valid.1 > > (The recover part of the program's now larger functionality runs > > only on DOS though, not on Unix, as DOS passes filled buffers back > > even when read() returns CRC error, whereas FreeBSD discards the > > buffer content on error. > > > > Julian > --------------------- > > Date: Wed, 9 May 2001 09:11:58 +0200 (MET DST) > > Message-Id: <200105090711.f497Bwr27407@uriah.heep.sax.de> > > From: j@uriah.heep.sax.de (J Wunsch) > > Subject: Re: Recovered data with positive head offset field replaceable unit msg > > To: freebsd-scsi@FreeBSD.ORG > > > > Arranging for a `read track' functionality in the FreeBSD floppy > > driver should be possible. This will return you the entire /bit/ > > contents of the track, no CRC checks &c. Only the first sector ID > > will be synchronized, the remainder of the track is returned as it > > appears on the floppy; you need to manually bit-dealign and perhaps > > bit-reverse the remaining data. > --------------------- > > Hi Joerg, > Thanks, > Doing a track was what Greg L suggested to brian@CSUA.Berkeley.EDU, > however that sounds like more work, & not optimal maybe ? > In 1987 with DOS I was lucky, I did a read() on each sector, copied each > sector with a good CRC to hard disc, & only repeat tried > bad floppy sectors, doing a statistical average of each bit, > (if none of the reads gave me a good CRC). > (I also did multi sectors initially, then dropped to single sectors on error). > To avoid head (*) wear & increase chance of a good CRC to the max, > I'd prefer to stick to doing single sector seeks & reads, not tracks. > (*) Forget media wear: I reccomend anyone who uses my valid.c > to read odd sectors a few hundred/thousand times off already bad media, > to discard media after reading :-) > In an ideal world with lots of free time ;-) Brian Julian or Joerg > would extend src/sys/isa/fd.c to support > http://bim.bsn.com/~jhs/src/bsd/jhs/bin/public/valid/valid.c :-) > > - > Julian Stacey Unix Consultant - Munich Germany http://bim.bsn.com/~jhs/ > Ihr Rauchen => mein allergischer Kopfschmerz ! Kau/Schnupftabak probieren ! > Like Linux ? Then also look at FreeBSD with its 5000+ packages ! > > > > > > > > > > > > > > > > > > > > > > > > > > sector, & though I got -1, the sector data was there (even if mangled) > > Julian > - > Julian Stacey Unix Consultant - Munich Germany http://bim.bsn.com/~jhs/ > Ihr Rauchen => mein allergischer Kopfschmerz ! Kau/Schnupftabak probieren ! > Like Linux ? Then also look at FreeBSD with its 5000+ packages ! > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-hackers" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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