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Teac FD-55FR 511U is a 720KB drive?

Shadow Lord said:
In what way? I have never seen a SD drive in actual use...
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It's not the drive that determines Single Density or Double Density but the controller and (in the early days of disk manufacture) the quality of the diskette itself. The drive just magnetizes and reads back bits on the disk, just like a cassette recorder that doesn't care whether it's playing or recording a symphony or a program for your C64.
 
MikeS said:
Finally, Chuck didn't say that a DD disk written in a HD drive will be unreadable in a 360K DD drive; it works just fine as long as you do NOT write on a given disk with both types of drive; once you've formatted or written on a disk with one drive type you can read it with either type no problem as long as any subsequent writing is done with the same drive type.
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I thought I said as much with this:

The compatibility problem deals with the fact that a 360K 5.25" drive head writes and reads a track that's twice as wide as that of a 720K/1.2M drive. If there was anything in the spaces between the alternate tracks that a 1.2MB drive writes in 360K compatibility mode, a genuine 360K drive will pick this up as read noise and render the data written by the 96 tpi drive as garbage, even though the disk will continue to be readable on a 96 tpi drive.

There is, however a way around this problem if all you'd like to do is to create floppies readable on a 48 tpi drive using a 96 tpi drive. That is to degauss the floppy before formatting on the 96 tpi drive. Not many people have deguassers that will handle a floppy, however. (I use a VHS tape bulk eraser myself). The S/N ratio isn't quite as good as a real 48tpi disk, but it'll be fine for most uses.
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Note that even a mixed-write disk will always be readable on a 96 tpi drive. So if you get a "360K" disk that has problems being read in a 360K drive, try it in a 96 tpi (HD) drive.

Conversely, since the S/N ratio is better with a 360K drive (and the radial alignment is a little less touchy), a marginal 360K disk that has problems being read on an HD drive might just be readable on a 360K drive.

So it's good to keep both drive types around.

Where I'm seeing more confusion nowadays is with the difference between DS2D/DD/QD media and DSHD media. The beehive collective memory has faded enough that to some folks 5.25" media is 5.25" media. This can get nasty.

I can recover data with a high degree of success from an HD floppy written as a DD disk (i.e. 360K on a 1.2M disk), but the other way around (HD on a DD floppy) is hopeless. You can usually get the first 20 cylinders or so, then the error rate increases dramatically and by the time you're to cylinder 40, nothing is recoverable. If you look at the flux-change histogram on the inner-half cylinders of such a disk, there are no high-frequency components left to recover.

The nasty part is that this "blurring" of data happens with time. So for a day or so, the disk might look usable, but by the time you're a month out, it's too late.
 
Chuck(G) said:
I thought I said as much with this:..
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You did indeed, and very clearly, but it looked like you might still have been misunderstood:
But as Chuck(G) pointed out the difference in writing will still make the disk unreadable in a nl 360KB drive.
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That depends on whether it had previously been written to with a DD drive.
Where I'm seeing more confusion nowadays is with the difference between DS2D/DD/QD media and DSHD media. The beehive collective memory has faded enough that to some folks 5.25" media is 5.25" media. This can get nasty.
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Especially since AFAIK you can not always rely 100% on the presence or absence of a reinforcing ring, can you?
 
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Shadow Lord said:
1. What systems ever used this format? I am pretty sure it was not an IBM compatible system.
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Tezza mentioned TRS-80. Another kind of system where your drive might prove useful is with a BBC Micro which would format .. um, is it 200K per side, 80 tracks for a total capacity of 400K with DFS? I think ADFS does up to 640K for a double sided 80 track floppy disk, or perhaps I'm mixing it up with the 3.5" formats.

There were several other systems which used similar 80 track drives, but perhaps not with the same interface as yours. Actually a friend of mine just recently was looking for exactly the kind of drive that you seem to have in possession, but I don't know if he found anything yet.
 
MikeS said:
Especially since AFAIK you can not always rely 100% on the presence or absence of a reinforcing ring, can you?
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That's very true--I've both types of media with and without reinforcing rings--although why any manufacturer would put a ring on HD media is beyond me. The rings were introduced at a time when hub clamp mechanisms on 5.25" were still evolving and you could really mess up the hub area with an old drive if you weren't careful. By 1980 or so, this had all been worked out.
 
carlsson said:
Actually a friend of mine just recently was looking for exactly the kind of drive that you seem to have in possession, but I don't know if he found anything yet.
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Well, as was discussed any 1.2MB HD drive with the appropriate jumpers would be equivalent and probably much easier to find; even without the right jumpers it's often possible to change the speed on the motor PCB directly (see Dave Dunfield's site for a writeup) and permanently set to DD with pin 2; the only other issue might be Ready vs Disk Change, but almost every drive has a jumper position for that.
 
MikeS,

No I followed Chuck(G)'s explanation. The wiki article pretty much said the same thing. The scenario I was looking at involved taking old 360KB disks from my XT and writing to them on the 1.2MB drive. This would then make them not work on the XT anymore. I am sure I have already "ruined" a few disks since i had heard of this issue back in the day but never paid attention to it nor fully understood it until now. Yes the disks are still readable in my 1.2MB drive and if i hookup a 360KB drive I can transfer them to 360KB disks that can be read in my XT machine!

On another note I scavenged FD-55GFR from one of my other machines and now have access to my 5 1/4 floppies. I also found a bit of info on Jumper Settings at this archive.

View attachment Teac FD-55GFR-149-U Jumper Settings.pdf

I cleaned it up a bit and made it into a PDF. If anyone w/ more knowledge then me would be kind enough to look at it to make sure it is accurate I'd be happy to post it out in the cloud somewhere. Thanks!
 
Anders,

Thanks for the info.

carlsson said:
Actually a friend of mine just recently was looking for exactly the kind of drive that you seem to have in possession, but I don't know if he found anything yet.
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If your friend is still looking for the drive he is more than welcome to mine for my original cost + shipping assuming he is in the USA. If not, the cost of shipping can be proibitive for small item like this.
 
Chuck(G) said:
I'd have to go digging a bit--it must have been around 1988-89 or so. I did write a later one that adds an extra 1K sector to 1.44M 3.5" floppies to create a phantom 160K drive. I know I've got that one pretty much at hand.
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If you ever find either and care to post either I'd be interested to take a look. It could be a very cool way to setup a PW/Disk Lock mechanism...
 
Shadow Lord said:
MikeS,
No I followed Chuck(G)'s explanation.
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Sorry, I should have read the context more carefully.
I cleaned it up a bit and made it into a PDF. If anyone w/ more knowledge then me would be kind enough to look at it to make sure it is accurate I'd be happy to post it out in the cloud somewhere. Thanks!
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Thank you! Looks OK to me at a fast perusal.
 
Chuck(G) said:
Teac drive coding (the letter after the number) is fairly specific. Combinations of letters mean that the drive can support both types of media. The numbers before the letter dictate the physical size of the meidum. Letters and numbers after that indicate other features (e.g. right-hand latch lever, locking mechanism, head-load solenoid, bezel color, electronics version, SCSI interface, etc.).

The more common capacity letters are:

B = 360K (DS2D)
F = 720K (DS2D)
G = 1.2MB (DSHD)
H = 1.44MB (DSHD)
J = 2.88MB (DSED)

The common size codes run as follows:

35,135,235,05 = 3.5"
5, 45, 55, 155 = 5.25"

So the bog-standard 360K 1/2 height 360K drive is the FD55B. The usual 1.2MB drive is FD55GF (because it supports both 1.2M and 720K formats). A half-height 5.25" 720K drive is an FD55F. A third-height 720K 3.5" drive is a FD23F; a 3-mode (720, 1.2M, 1.44M) one-third hieght 3.5" drive is an FD235HG. A 2.88MB 3.5" drive is an FD235J.
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I know this is an old article, but I'm hoping someone knows what the other suffixes mean. For example, I've seen a FD-55FR and FD-55FV, in addition to the standard FD-55F. I've looked for a while, on what R or V would mean, but I couldn't find anything.

Thanks.
Mark
 
A perfectly aligned 80 track drive can be used to read and write 40 and 80 track formats. A perfectly aligned 40 track drive will still read disks written on a 80 track drive, even though the tracks are written much more narrowerly by the 80 track drive. The drives used have to be perfectly aligned (not a problem for me since I align drives). I still do this all the time on my Compupro S-100 system using a Utility Compupro named New Media and Mitsubishi M4853 5.25" 800K 80-track drives.

There was also a Drive Utility that was published by New Generation Systems which used a Suntronics S-100 disk controller card controlling both 8" dsdd and 5.25" dsdd 80 track drives to rear and write over 500 different 8" and 5.25" disk formats. I never tried it with 5.25" 1.2mb drives because there weren't a bunch of different formats like there were for computers with 48TPI and 96TPI 5.25" drives.

Morrow Designs also included a format reading/changing utility with the Morrow MicroDecision, and KayPro also bundled a format changing program with their big metal luggables.

When PC compatibles took over the market, the many different formats disappeared along with diversity in the market. I don't think the newer stamped sheet metal frame floppy drives are made with the same precision as their older cast aluminum frame cousins, but they sure are cheaper. New drives right out of the box don't appear to be aligned as well as older drives were. So maybe if you tried to use one of them with a format changing program, you wouldn't have the same luck.
 
As long as you use the correct diskette type an 80 track drive can indeed read and write 40 and 80 track formats and a 40 track drive will probably be able to read a 40 track disk written on an 80 track drive as long as it has not previously been written on a 40 track drive.

There are several excellent programs to read foreign formats on a PC, including 8" diskettes, as long as the controller and drive can handle the format in question; with the right controller and software a 1.2HD drive can handle many of them (most CP/M, 160,180,320,360,720,1200, etc.) except for 100TPI, hard sectored, variable speed GCR etc.
 
My Tandy 2000 also uses the 720K format on 5.25". Its a bit of a pain but there are special utils so that makes live a little easier :)
 
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