gejohann@uokmax.ecn.uoknor.edu (Gene Edward Johannsen) (10/16/89)
I've got problems. Recently my FAT has become _slightly_ messed up. It's not because of a virus or anything. Its just one of those things that happen now and then. The error causes CHKDSK to think that my C: drive is not a DOS disk and the Norton Utilities doesn't think my C: drive is a hard disk, except for the DISK TEST program that doesn't see anything wrong at all. Anyway, I know that there are two copies of the FAT on my disk and everything works okay using the backup, I would still like to fix my FAT--without reformatting if possible. The closest thing I get to an actual error message occurs when I attempt to run DOG (a disk organizer program) that returns INVALID CLUSTER when it tries to read the FAT. All help will be greatly appreciated. Thanks. Gene
BL.JPL@forsythe.stanford.edu (Jonathan Lavigne) (10/19/89)
In article <1989Oct15.220849.21435@uokmax.ecn.uoknor.edu>, gejohann@uokmax.ecn.uoknor.edu (Gene Edward Johannsen) writes: > >I've got problems. Recently my FAT has become _slightly_ messed up. It's >not because of a virus or anything. Its just one of those things that happen >now and then. The error causes CHKDSK to think that my C: drive is not a DOS >disk and the Norton Utilities doesn't think my C: drive is a hard disk, except >for the DISK TEST program that doesn't see anything wrong at all. > >Anyway, I know that there are two copies of the FAT on my disk and everything >works okay using the backup, I would still like to fix my FAT--without >reformatting if possible. I, too, recently had a problem with the FAT on my hard disk. CHKDSK gave the "Probable non-DOS disk " message and, for some reason, the settings in my CONFIG.SYS file didn't take effect. Someone told me to see whether the first two bytes of the FAT were "F8FF". In fact, they were "F7FF". Since the same person said he didn't think the FAT problem had any effect on my CONFIG.SYS difficulties, I decided to reformat my disk anyway. After I did, all the problems vanished, and, sure enough, the first two bytes in the FAT now read "F8FF". If the first two bytes in the two copies of the FAT on your hard disk aren't "F8FF", you might try changing them using Norton or something similar. Of course I wouldn't do anything of that kind without backing up the disk and assuming that I might have to reformat. Jonathan Lavigne BL.JPL@RLG.STANFORD.EDU Research Libraries Group Stanford University
greiner@oahu.cs.ucla.edu (John Greiner) (10/20/89)
In article <1989Oct15.220849.21435@uokmax.ecn.uoknor.edu> gejohann@uokmax.UUCP (Gene Edward Johannsen) writes: > >I've got problems. Recently my FAT has become _slightly_ messed up. It's >not because of a virus or anything. Its just one of those things that happen >now and then. The error causes CHKDSK to think that my C: drive is not a DOS >disk and the Norton Utilities doesn't think my C: drive is a hard disk, except >for the DISK TEST program that doesn't see anything wrong at all. I ran into this problem myself a while back and spent a lot of time tracking down the problem (and learned alot about hard disks on the way). According to Microsoft, the first byte in each copy of the FAT table is a Media Descriptor byte. This byte is used to identify the type drive to DOS. Though only the first FAT table is usually accessed for this info, even there it is rarely used. Apparently, there is another copy of this value in the boot sector (or is it the partition table?). Some programs look at one, other programs the other. If one value gets corrupted to a value that doesn't have a meaning defined by Microsoft, a program may consider the disk to be a non-DOS disk (as chkdsk does). Other programs which are only looking to see if the value corresponds to the value(s) assigned to hard disk formats, may, upon detecting a corrupted value, declare the drive not to be a hard drive. Programs which look to the other location for the Media Descriptor byte will run just fine. Microsoft gave me this information (as well as the location of the Media Descriptor byte in the boot sector/partition table, but I don't have the letter with me...). If you have access to Norton Utilities, you can check the first byte of the 1st FAT table (make sure to use hex mode, not the fat table editor as it doesn't show the Media Descriptor byte). It should be F8 for most hard drives, but I can't be certain that's what it should be for yours. In my case, I changed it to F8, and the symptoms you described dissappeared. -John Greiner
MLAB1@kuhub.cc.ukans.edu (10/20/89)
In article <5254@lindy.Stanford.EDU>, BL.JPL@forsythe.stanford.edu (Jonathan Lavigne) writes: > In article <1989Oct15.220849.21435@uokmax.ecn.uoknor.edu>, > gejohann@uokmax.ecn.uoknor.edu (Gene Edward Johannsen) writes: >> >>I've got problems. Recently my FAT has become _slightly_ messed up. It's >>not because of a virus or anything. Its just one of those things that happen >>now and then. The error causes CHKDSK to think that my C: drive is not a DOS >>disk and the Norton Utilities doesn't think my C: drive is a hard disk, except >>for the DISK TEST program that doesn't see anything wrong at all. >> >>Anyway, I know that there are two copies of the FAT on my disk and everything >>works okay using the backup, I would still like to fix my FAT--without >>reformatting if possible. > I, too, recently had a problem with the FAT on my hard disk. CHKDSK > gave the "Probable non-DOS disk " message and, for some reason, the > settings in my CONFIG.SYS file didn't take effect. Someone told me > to see whether the first two bytes of the FAT were "F8FF". In fact, > they were "F7FF". Since the same person said he didn't think the FAT > problem had any effect on my CONFIG.SYS difficulties, I decided to > reformat my disk anyway. After I did, all the problems vanished, > and, sure enough, the first two bytes in the FAT now read "F8FF". If > the first two bytes in the two copies of the FAT on your hard disk > aren't "F8FF", you might try changing them using Norton or something > similar. Of course I wouldn't do anything of that kind without > backing up the disk and assuming that I might have to reformat. > > Jonathan Lavigne BL.JPL@RLG.STANFORD.EDU > Research Libraries Group > Stanford University
johnlee@pnet07.cts.com (John Wiley) (10/21/89)
Jonathan Lavigne writes: >If the first two bytes of the FAT on your hard disk aren't "F8FF" The first byte of each copy of the FAT is called the "Media Descriptor Byte," and you're right - it should be F8 according to "THE MS-DOS ENCYCLOPEDIA" by Duncan. He also points out that this same value should be found in the "Boot Record," which is logical sector 0 of the partition (on most C: drives, that's BIOS sector 1, Track 0, Side 1). Offset 15 hex (21 decimal) is the location of the Media Descriptor in the Boot Record (counting from offset 0). If you do try fixing the Media Descriptor Byte in the FATs, it would be good to check the one in the Boot Record too. Assuming you can get it to work, it would be a good idea to back it up and do a low-level format. That's the best insurance for future data integrity. -good luck. UUCP: nosc!pnet07!johnlee (John Wiley - San Diego, CA.) ARPA: simasd!pnet07!johnlee@nosc.mil INET: johnlee@pnet07.cts.com
mitch@fedeva.UUCP (Mitch Wood) (03/01/90)
Help! I am having a FAT problem on my 40 meg hard drive. One of the FAT's has gotten corrupted, and I dont know what software to use to fix it! The copy of the FAT is ok (that's what chkdsk says). So I am still running but I want to fix the problem before it gets too bad to fix. I have already backed up the drive... just reformatting it does not fix it (low or high) I must have gotten a new bad spot on the disk? Chkdsk /F does not fix it? why? Advice needed quickly! Thanx Mitch Wood -- +---------------------------------------------------+----------------------+ ! Mitch Wood @ FEDERAL EXPRESS Memphis, TN # "Ok you guys, quit ! ![..!hplabs!csun,..!mit-eddie!premise]!fedeva!mitch # clowning around and..! +---------------------------------------------------+----------------------+