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5.25" floppy disks with bad sectors - any solutions?

kishy

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Windsor, ON Canada
I have gone through the last couple days extensive testing (basically, Scandisk and a format with two different drives on the same set of disks) on the majority of my 5.25" floppy disks. All disks are DS/DD except a couple which are those oddball 96tpi disks (I don't even know what you call those). All were and are formatted as 1.2mb.

The reason for the testing was the high rate of errors I was finding the last time I used them. "Data error reading drive B", "General failure reading drive B", "Seek error reading drive B" and the like.

The results are not surprising, and not good. All of them are at least 50% bad sectored, giving me (in effect) a pile of unreliable 360k disks...

I sort of doubt it, but is there any sort of magic repair solution for these? Perhaps some kind of waving pattern with a magnet?

Once bad sectors start developing, my understanding (and experience) is that the affected disk will just keep getting worse with time, whether it is used or not, so they're basically trash from the time the first bad sector develops.

Any ideas? If it's a hopeless cause I'll turn them into some kind of decoration.

Oh, and I have a never-opened box of Fujifilm 5.25" disks with a lifetime replacement warranty based on manufacturer defects. Given that the package has never been opened, wouldn't anything wrong with them technically be a manufacturer defect? I wonder if Fujifilm is prepared to back up that warranty...
 
Clean the heads on your floppy drives. A lot of errors are transient and are caused by dirty drive heads. Clean and lubricate the rails on the drive as well. Poor track positioning can lead to read errors. Finally, if it is data you need to recover try another drive. Slight differences in head alignment can make a difference.

If this is just a matter of deciding whether to throw a diskette away or not, a bulk eraser might help. If the diskette has developed a physical error it will probably never be curable though.
 
If the diskette was written 20 years ago with no errors on anything less than floor sweepings, it's probably readable with no or very few errors today. After thousands of diskettes, that's my experience.

First off, clean the drive heads. When you're resurrecting old floppies, this needs to be done frequently, as old media does shed and gunk up the heads.

One thing that we see is diskettes written on drives with alignment problems. If they were formatted and written on misaligned drives, they'll have to be read with misaligned drives.

If you have an oscilloscope, also check the bitrate of the recorded data and adjust your reading drive spindle speed accordingly, if need be.

Floppies, particularly DSDD 5.25" and 8" are extremely reliable if the coating manages to stay stuck to the cookie substrate.

Finally, if your 360K floppies were written on a 1.2M drive, you'll need to read them on a 1.2M drive--or at least a 96 tpi drive.

720K and 1.44M floppies use much thinner coatings and recovery is much less a certain proposition.
 
Clean the heads on your floppy drives. A lot of errors are transient and are caused by dirty drive heads. Clean and lubricate the rails on the drive as well. Poor track positioning can lead to read errors. Finally, if it is data you need to recover try another drive. Slight differences in head alignment can make a difference.

If this is just a matter of deciding whether to throw a diskette away or not, a bulk eraser might help. If the diskette has developed a physical error it will probably never be curable though.

I use multiple drives to try to reduce the chance of that being an issue (I said 2 in the original post, but it's actually 6, though I do recognize the issue of head misalignment - fortunately all drives are able to read each others disks). These are disks which, prior to me getting them, were stored extremely poorly.

I'd, of course, still like to clean the heads on the drives.

If the diskette was written 20 years ago with no errors on anything less than floor sweepings, it's probably readable with no or very few errors today. After thousands of diskettes, that's my experience.

First off, clean the drive heads. When you're resurrecting old floppies, this needs to be done frequently, as old media does shed and gunk up the heads.

One thing that we see is diskettes written on drives with alignment problems. If they were formatted and written on misaligned drives, they'll have to be read with misaligned drives.

If you have an oscilloscope, also check the bitrate of the recorded data and adjust your reading drive spindle speed accordingly, if need be.

Floppies, particularly DSDD 5.25" and 8" are extremely reliable if the coating manages to stay stuck to the cookie substrate.

Finally, if your 360K floppies were written on a 1.2M drive, you'll need to read them on a 1.2M drive--or at least a 96 tpi drive.

720K and 1.44M floppies use much thinner coatings and recovery is much less a certain proposition.

The disks in question were all sold blank and then written by the end user, and have all been stored poorly (all of the misperforming ones that is - I have some pristine ones that were, accordingly, stored perfectly).

The disks are not 360k - they are 1.2's which have about 360k usable space on account of the bad sectors (physical damage, correct?).

Because the disks have bad sectors (which are marked as bad sectors), does this rule out the dirty drive issue? Even if I clean the drive heads it will make no differences, the sectors are still marked bad. Is there, by chance, a way to un-mark the bad sectors and then rescan the disks with the newly cleaned drive? (thought process at work here: if a dirty drive thought the sector was damaged because of the drive heads being dirty, not the disk being bad, then it would mark a GOOD sector as being bad anyway)

Can anyone recommend a decent guide for drive cleaning? Or alternatively tell me if the procedure I already know is correct or not: qtip, isopropyl alcohol, dabbing motion on heads (NOT rubbing action).

edit: pics show a couple of the EXTREME cases (the last one is actually a 360k, but it's one of only one or two in the lot)

http://img44.imageshack.us/img44/6484/badsectors1.jpg
http://img121.imageshack.us/img121/3460/badsectors2.jpg
http://img121.imageshack.us/img121/5070/badsectors3.jpg
 
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All disks are DS/DD except a couple which are those oddball 96tpi disks (I don't even know what you call those). All were and are formatted as 1.2mb.

I am confused. If the floppies are only double density, why are you formating them to 1.2MB (high density)?
 
I am confused. If the floppies are only double density, why are you formating them to 1.2MB (high density)?

That had me scratching my head. Trying to fromat DSDD to DSHD will produce exactly these results. The coating on a DSHD has completely different characteristics (coercivity, thickness, particle size, loading, etc.).
 
I am confused. If the floppies are only double density, why are you formating them to 1.2MB (high density)?

I didn't format them to 1.2; they came to me already as 1.2 (so naturally if I run format without any switches it will format to 1.2 again). As far as I was aware there was no such thing as a high density 5.25" floppy and that DD was in fact 1.2MB. Obviously my understanding was flawed (but let's keep in mind this stuff was already going out the window around the time I was born).

That had me scratching my head. Trying to fromat DSDD to DSHD will produce exactly these results. The coating on a DSHD has completely different characteristics (coercivity, thickness, particle size, loading, etc.).

That does make tons of sense (now knowing my flawed understanding); I did however not know that DSHD even existed to begin with (in the case of 5.25's)

My comment about "oddball" 96tpi disks is because they are a minority in the disks I have and are marked as being 1.6MB, which my drives can't format (or at least the format command can't format).
 
My comment about "oddball" 96tpi disks is because they are a minority in the disks I have and are marked as being 1.6MB, which my drives can't format (or at least the format command can't format).

Those 96tpi disks are the only ones that actually can be properly formated as 1.2MB disks. The rest are problably 48tpi (Double Density = 360Kb).
 
Those 96tpi disks are the only ones that actually can be properly formated as 1.2MB disks. The rest are problably 48tpi (Double Density = 360Kb).

Aw crap, so I've (or more likely the previous disk owners) basically destroyed a bunch of 360k disks?
Live and learn I guess...

What process, if any, could I go through to get these back to a usable state?
For example, unmark "bad sectors" (which probably aren't bad at all, since they don't exist) then format with the /4 switch (360k)?

Edit:
format b: /4 /c
then scandisk it, there's nothing wrong with the disks

Someone slap me, please?
 
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Bulk erase, then format with the correct format for the density of the disk ...
 
Bulk erase, then format with the correct format for the density of the disk ...

My apologies, my edit must have been too late before your reply.

One point though...if DSHD is 1.2 and DSDD is 360k, but 96TPI is 1.2...

I have DSDD disks with 96TPI, what should these properly be formatted as?
 
Like I said, 5.25" (360K) diskettes are very reliable--not as reliable as 8" in my experience, but the differential is mostly due to bargain brand diskettes with lousy coatings (e.g. Wabash).

I wish I could say the same about most 3.5" DSHD media.
 
We've got two different parameters to worry about.

The magnetic coercivity (http://en.wikipedia.org/wiki/Coercivity) of a material determines what kind of 'force' is required to leave an imprint on the material. High density diskettes use a different materials. There is a good table here: http://en.wikipedia.org/wiki/Floppy_disk_format .

The other parameter is the tracks per inch. The tracks per inch is a function of the drive and the head size on the drive, not the media. (Up to a certain point that is, but lets go crazy.) The good old double density 5.25 inch drive capable of 360KB per drive only writes 40 tracks per side because the drive heads are so damn big! With a smaller drive head, you could write more tracks per side. Consider the high density 5.25 inch drive - it has a narrower head capable of writing 80 tracks per side.

Under software control you can use a 1.2MB drive to write 80 tracks per side to double density media. That effectively doubles the capacity of a 360KB (double density) diskette, not through magic but by just simply using a narrower drive head. This wasn't a standard format, so it's not going to be readable unless you use the same software to read it back. (Fdformat did this.) These diskettes will also be unreadable in a standard double density (40 track) drive.


Mike
 
The magnetic coercivity (http://en.wikipedia.org/wiki/Coercivity) of a material determines what kind of 'force' is required to leave an imprint on the material. High density diskettes use a different materials. There is a good table here: http://en.wikipedia.org/wiki/Floppy_disk_format .

It's far more complicated than that, Mike. Not only the coercivity of the material (e.g. Iron oxide vs. Barium ferrite), but the thickness of the coating (at higher data rates, a too-thick coating increases bit-shift issues), the particle size (must be small enough to support smaller bit cells) and the "loading" or the ratio of magnetic material to binder (high density diskette generally have much lower loading, which is one reason that their coatings appear to be almost transparent).

A new degaussed 5.25" HD floppy can sometimes be used in a pinch as DD media. When I get one mixed into a batch of DD media for conversion, I get sweaty palms, but most often, they do seem to work, even after 20 years of sitting around.

As far as "standard" formats go, the PC 720K 3.5" format will work fine on a 1.2MB drive using DD diskettes, provided that you have a driver to overcome the stupidity of the BIOS. Lots of vendors made 80 cylinder DD (sometimes called QD) drives and you could buy diskettes that were verified for QD use. There were a few "clone" BIOSes that could handle 720K 5.25" in a 1.2M drive without any special software.

All in all, I admire NEC's 9800 series of PCs. They started with 8" and moved to 5.25" and then to 3.5"--with all having exactly the same logical format--all spin at 360 RPM and use the same data rate.
 
Like I said, 5.25" (360K) diskettes are very reliable--not as reliable as 8" in my experience, but the differential is mostly due to bargain brand diskettes with lousy coatings (e.g. Wabash).

I wish I could say the same about most 3.5" DSHD media.

I am kind of surprised by this reliability - the fact that these disks were stored in quite poor conditions for years, then sat by me next to unshielded speakers for years (before I knew any better!), formatted to an incorrect format and then formatted back (and used in tons of drives) definitely does attest to the 'build quality'.

So it's not my imagination that 3.5" 1.44 disks seem to have a high failure rate...at least the ones I use all the time. Fortunately I have tons of them and people throw them at me by the bucketful, so even if I only get one last use out of a disk (be it for a bootdisk or moving a DOS game somewhere or whatever) it's not a total disaster. All of my actual data STORAGE is done on external hard drives and optical disks, I only use floppies for transporting stuff between floppy-only computers.

We've got two different parameters to worry about.

The magnetic coercivity (http://en.wikipedia.org/wiki/Coercivity) of a material determines what kind of 'force' is required to leave an imprint on the material. High density diskettes use a different materials. There is a good table here: http://en.wikipedia.org/wiki/Floppy_disk_format .

The other parameter is the tracks per inch. The tracks per inch is a function of the drive and the head size on the drive, not the media. (Up to a certain point that is, but lets go crazy.) The good old double density 5.25 inch drive capable of 360KB per drive only writes 40 tracks per side because the drive heads are so damn big! With a smaller drive head, you could write more tracks per side. Consider the high density 5.25 inch drive - it has a narrower head capable of writing 80 tracks per side.

Under software control you can use a 1.2MB drive to write 80 tracks per side to double density media. That effectively doubles the capacity of a 360KB (double density) diskette, not through magic but by just simply using a narrower drive head. This wasn't a standard format, so it's not going to be readable unless you use the same software to read it back. (Fdformat did this.) These diskettes will also be unreadable in a standard double density (40 track) drive.


Mike

Definitely some handy info there, though I'll confess to already knowing the differences between the older and newer drives (head width). I have actually looked at the Wikipedia article on floppy disk formats just the other day and found it "must be incomplete" on the basis of "DSDD floppies being 1.2mb" (which while I now know to be false, before today I did not).

I do though have a disk here which is labeled, on the original sticker:
-DSDD/DFDD
-96 T.P.I.

(the label is bilingual English/French explaining DFDD)

As far as I can tell, this combination doesn't exist. If the disk is formatted to 1.2mb it has about 100k usable space because of "bad sectors", formatting to 160k causes it to work seemingly properly but a 160k disk at 96tpi? I imagine the drive is using whatever the "default" track per inch preference is so the fact the disk "can support up to 96tpi" is kind of useless.

I'm just trying to figure out what this disk was intended for. This particular disk actually appears to have originally contained software, "Axiom Educator 940".

How do we get TPI into tracks per side?
 
How do we get TPI into tracks per side?

I despise the term "track" when what one really means is "cylinder"--the only time they are equivalent is when we're talking about single-sided media. Generally 48 tpi = 40 cylinder, 96 = 80 cylinder, 100 tpi = 77 cylinder. While 48 and 96 share the same "track 0" position, 100 does not.

If you want to fool around with quad-density recording on DD diskettes using a 1.2MB drive, try the attached driver.
 

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It's far more complicated than that, Mike. Not only the coercivity of the material (e.g. Iron oxide vs. Barium ferrite), but the thickness of the coating (at higher data rates, a too-thick coating increases bit-shift issues), the particle size (must be small enough to support smaller bit cells) and the "loading" or the ratio of magnetic material to binder (high density diskette generally have much lower loading, which is one reason that their coatings appear to be almost transparent).

A new degaussed 5.25" HD floppy can sometimes be used in a pinch as DD media. When I get one mixed into a batch of DD media for conversion, I get sweaty palms, but most often, they do seem to work, even after 20 years of sitting around.

As far as "standard" formats go, the PC 720K 3.5" format will work fine on a 1.2MB drive using DD diskettes, provided that you have a driver to overcome the stupidity of the BIOS. Lots of vendors made 80 cylinder DD (sometimes called QD) drives and you could buy diskettes that were verified for QD use. There were a few "clone" BIOSes that could handle 720K 5.25" in a 1.2M drive without any special software.

All in all, I admire NEC's 9800 series of PCs. They started with 8" and moved to 5.25" and then to 3.5"--with all having exactly the same logical format--all spin at 360 RPM and use the same data rate.

Chuck,

There comes a point where one has to resist being overly verbose and beating a subject to near death. For the purposes of this conversation (paraphrased as 'I've got some bad diskettes') highlighting the fact that the material is different and has different properties was probably sufficient. Hence, I didn't go further ..


Mike
 
As far as I can tell, this combination doesn't exist. If the disk is formatted to 1.2mb it has about 100k usable space because of "bad sectors", formatting to 160k causes it to work seemingly properly but a 160k disk at 96tpi? I imagine the drive is using whatever the "default" track per inch preference is so the fact the disk "can support up to 96tpi" is kind of useless.

I'm just trying to figure out what this disk was intended for. This particular disk actually appears to have originally contained software, "Axiom Educator 940".

Those disks were intended for a system that had a 720kB 5.25" drive. The Tandy 2000 was probably most common model that shipped with such a drive but lots of other systems had one before the "HD" 1.2 MB format got established.
 
I despise the term "track" when what one really means is "cylinder"--the only time they are equivalent is when we're talking about single-sided media. Generally 48 tpi = 40 cylinder, 96 = 80 cylinder, 100 tpi = 77 cylinder. While 48 and 96 share the same "track 0" position, 100 does not.

If you want to fool around with quad-density recording on DD diskettes using a 1.2MB drive, try the attached driver.

Properly naming/labeling things is important, though in my case I don't know what I mean. My understanding (though easily and likely flawed) is that sectors go back-to-back inside of tracks, and that a track is a circular "path" around the disk, and that a cylinder refers to some unknown alternate way of referring to tracks. I remember looking that up and having limited luck finding a detailed description when I was trying to understand exactly where to park the heads on an RLL drive (some park utils asked for it as a track, some as a cylinder, and the number was different depending on which it asked for).

77 cylinders is...an 8 inch floppy?

Driver downloaded; will tinker with it at some point. Given that I'm currently working with my "patented computer-on-a-tray-table, boots-off-98se-boot-floppy with no nonremovable storage" computer, this might prove somewhat difficult, but I'll find a way.

Chuck,

There comes a point where one has to resist being overly verbose and beating a subject to near death. For the purposes of this conversation (paraphrased as 'I've got some bad diskettes') highlighting the fact that the material is different and has different properties was probably sufficient. Hence, I didn't go further ..


Mike

Chuck, I actually never saw the post Mike replied to...sorry if I seemed to disregard it.

Mike, perhaps we define "overly verbose" differently. I have yet, in all my travels of the vast internet, to find an explanation of floppy disk drives and floppy disk media that completely, clearly and **in language that I will not then have to go and immediately research, sending me on a wild goose chase** gives me an understanding that prevents such misunderstandings as "DSDD = 1.2MB". I am by no means criticizing your input in this thread - I am explaining why I don't already "get it" and as a result why I still don't "get it" entirely.
 
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Those disks were intended for a system that had a 720kB 5.25" drive. The Tandy 2000 was probably most common model that shipped with such a drive but lots of other systems had one before the "HD" 1.2 MB format got established.

Ohh, alright. Thanks.
Now the question is, is it my HD drives not supporting 720k, or is it the DOS 7 format command not supporting 720k (or is it both?)

I try format b: /f:720 and it says not supported.
 
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