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1.2mb floppy in 360kb drive?

J

jesuisdvd

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Apr 24, 2011
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Buenos Aires, Argentina
Hey guys, i got recently a computer (8088) and what i need is to try the floppy drive, to check if it works fine, but the problem is i only have 1.2mb 5,25" [regular] floppy disks, there's anyway to check the drive with those disks? because when i do B:\ with the disk on, it says abort, retry, or fail:mad:
 
jesuisdvd said:
1.2mb 5,25" [regular] floppy disks, there's anyway to check the drive with those disks?
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No.

High density 5.25" disks can not be formatted low density and vice versa. The magnetic surfaces are different. If you try, the DOS formatter will usually fail and leave the disk in an unformatted state. Some other formatters can be told not to very while formatting and appear to succeed, but the result will be full of errors - it would be totally pointless to test a drive with a disk like that.

I'm assuming you already have the computer up and running and all you need to do is just format a disk and write/read something with it to test it.
 
If you have a bulk eraser, degauss the disk first. It should work then--I've recovered quite a few 1.2MB floppies years after they were formatted when new to a DD format. Not the best for permanent retention but it can be made to work.
 
1.2 MB high density disks have a much higher coercivity (magnetic field strength) than 360 KB double density disks, so the DD format isn't strong enough to write to a HD disk and will usually fail with a "Track 0 bad - disk unusuable" error. Even if it does attempt to format, it'll get a lot of bad sectors and any data written to the disk will almost immediately become unreadable.

Coercivity of floppy disk types:

8" all formats: 300 oersteds

5.25" double density (360 KB): 300 oersteds
5.25" quad density (720 KB): 300 oersteds
5.25" high density (1.2 MB): 600 oersteds

3.5" double density (720 KB): 665 oersteds
3.5" high density (1.44 MB): 720 oersteds
3.5" extra-high density (2.88 MB): 900 or 1200 oersteds (unconfirmed)
 
Well, some can sit around and make pronouncements, but I thought I'd back my words up with action.

I grabbed three different DSHD 5.25" floppies out of my stock--a 'no name" duplicator grade one, a 3M labeled one, and finally, a Verbatim labeled one. All were NOS, never been used.

All failed to format on track 0 on a Teac FD-55-BR drive in an XT clone, complaining about "Track 0 Error". I then took each and carefully using my good old "Radio Shack High-Power Video/Audio Tape Eraser, Model 44-233A" I bulk erased each, starting with the eraser in contact with the floppy and moving in a circular motion, gradually brought the eraser to a foot away.

All formatted and wrote a full disk of files perfectly I used DOS 6.22 and FORMAT /u, xcopy and fc /b. I waited 15 minutes and repeated the fc verification step. No errors.

So, believe what you want, but I done it. :)

I suspect that a perfectly adequate bulk eraser could be constructed if you have access to a pile of neodymium magnets. After all, that's how cheap tape recorders did their erasing.
 
The degausser I'm using is pretty strong. I doubt that a CRT degausser can muster the field. Try it on a floppy you've written and see if it will erase it. My experience with permanent magnets shows that the magnet has to be practically in contact with the media to have an effect.
 
Using 360k media in a 1.2m drive can be tricky but is doable in many cases if you keep in mind the differences between the two largely incompatible formats. The track width is different. The track spacing is different. The magnetic field strength is different. If you have fresh unformatted media that has never been in a drive of the other type you can often format and use it in whatever type of drive you have if you mark it somehow and use it only in that type of drive. The worst case scenario is when you have a high density narrow track written right down the middle of a low density wide track. It's likely that neither type of drive will be able to read, write, or erase it. That's where the degausser comes in.

Some have mentioned that the actual magnetic emulsion on the mylar disk might be different. I suspect that that the higher end brand names might have used different formulations for the two types of disks in the early days but as everyone shifted to 3.5" disks and the 5.25" production started falling off the less reputable vendors probably didn't bother. Towards the "end of days" for all floppies I saw something similar happening with 720k vs 1.44m 3.5" media. One of my last buys was a box of 50 "white box" disks, allegedly formatted and tested at 1.44m at the manufacturer, from one of the bulk office supply retailers. The first clue was when files written to the disks were not readable. The second clue was when I noticed all 50 disks had the same "random" disk volume number. The third clue was when they all had significant numbers of bad sectors when reformatted on different drives and different machines. All 50 disks went into the trash.

In short, some of the media you will come across was crap when it was brand new. Years of use and storage in questionable environments didn't improve that. Media from the top names will probably be usable. Stuff made by the bottom feeders might not be worth your time.
 
DDS said:
In short, some of the media you will come across was crap when it was brand new.
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Some vendors were nice enough to put a warning label on the front to indicate that. For those that are not familiar, that highly technical floppy-jargon term is "Wabash". :happy10:
 
DDS said:
Using 360k media in a 1.2m drive can be tricky but is doable in many cases if you keep in mind the differences between the two largely incompatible formats.
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FWIW, this discussion has been about using 1.2M media in a 360K drive. :)

Furthermore, using 360K media in a 1.2M drive is not tricky at all. For me, at least, it works 100% of the time. It's using 360K media that has been formatted/written on a 1.2M drive in a 360K drive that (can) get tricky at times. Even then there are (I have some) 1.2M drives that can successfully format/write to 360K media so that the disks are useable in 360K drives without problem.
 
'that highly technical floppy-jargon term is "Wabash" '

Back when my Heathkit H89 was new I had a brand new right out of the box 5.25" disk from Inmac shed the emulsion the first time it was in the drive.
 
"Even then there are (I have some) 1.2M drives that can successfully format/write to 360K media so that the disks are useable in 360K drives without problem."

I suspect that would work with some drive combinations if you explicitly tell the 1.2m drive to format the disk as a 360k. Otherwise it would plop a 96tpi track right between each of the places where a 48tpi 360k disk would expect data to be found and the sector and track numbers would mostly not be what the 360k drive was expecting.

But I have found that some 360k drives will, for some reason, not read any disk I format in a 1.2m drive even when explicitly formatted as a 360k disk..

If you're trying to figure out the inner workings of disks and drives and their respective compatibilities, this can be entertaining. If you're just trying to get some files on to or off of a disk it can be a royal frustrating pain in the $#*.
 
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FWIW concerning writing to a 360 on a 1.2 drive, some do and some don't in my experience. On one of my 486 towers, I have both, 360 and a 1.2 drive. Problem solved.
 
Agent Orange said:
FWIW concerning writing to a 360 on a 1.2 drive, some do and some don't in my experience.
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Actually, they *all* do. The real question is whether or not a 360K drive can then *read* the product of the 1.2M's effort, because, without question, other 1.2M drives will be able to read that 360K disk that was made in the 1.2M drive.
 
Basically, my experiment was to show that, while floppy disks operate with full magnetic saturation (that is, where a stronger applied field does not result in more magnetization), it's quite possible to use a floppy in the linear, non-saturated area of a magnetization curve.

Coercivity is the measure of the strength of a magnetic field needed to reduce the fully-saturated magnetized material to zero. So an already-recorded 1.2MB 5.25" floppy has a high enough coercivity that the strength of the field from a 360K drive cannot overcome the already-present magnetization. The format and write fail.

However, audio and video tape recorders have operated for decades in the "linear" part of the magnetization curve, that is, they do not write at full magnetic saturation levels. Listening to a cassette recorded 32 years ago recently, I was surprised at how well it had held up (Dolby B recording didn't hurt either). So data recorded in the non-saturating part of the curve does not mysteriously "evaporate".

(As an aside, the part of the curve near zero magnetization is also quite non-linear, such that applying a stronger field doesn't result in proportionately more magnetization. That's why audio tape recorders use a "bias" of some sort to raise the lowest levels out of the "black hole" near zero magnetization).

So, in my example, I used a bulk eraser to reduce the bulk magnetization of a 1.2M floppy disk from saturation to near-zero, then proceeded to record my 360K data on the "linear" part of the magnetization curve. It'll probably be every bit as permanent as any other "real" 360K floppy--the S/N ratio will likely not be as good, though.

One could also increase the writing current on a "360K" drive to work wtih 1.2M media. Some duplicators wrote copies with higher-than-normal currents to improve the copy yield also.

Hope this clarifies things a bit.
 
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