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

[Shadow Lord]

O.k. I am confused. In my world IBM floppies went something like this:

5 1/4:
180KB SSDD - never really played w/ these except at old Apple labs in school. I believe the where the ones you could flip them to make them act like a manual DSDD disk.
360KB DSDD - Standard XT drive
1200KB DSHD - Standard AT drive

I bought a Teac FD-55FR thinking it was a 1.2MB drive. However, when I try to access a 1.2MB disk w/ it, there is an immediate "thuck" sound, an "Abort, Retry, Fail" and an
Int 24 Error. A bit of searching revealed that this could be a DSQD drive that can hold 720kb. Does anyone know if this is correct? If so:

1. What systems ever used this format? I am pretty sure it was not an IBM compatible system.
2. Can this drive do 1.2MB DSHD work?
3. If not, can it be configured to work as DSDD 360KB drive that can reliably read write 40 track disks?

Finally, out of curiosity does anyone know of a Teac 1.2MB floppy drive that did not use a latch mechanism but instead used an eject button similar to the one on 3.5" drives?

TIA!

p.s. I love how often our own Chuck(G) is referenced when one does a search on FDD and associated info!

 

[modem7]

I bought a Teac FD-55FR thinking it was a 1.2MB drive. However, when I try to access a 1.2MB disk w/ it, there is an immediate "thuck" sound

It could be due to a common issue with 5.25" drives that have sat unused for years - lack of, or solidified lubrication on the rails that the head assembly slides on.

 

[Shadow Lord]

It could be due to a common issue with 5.25" drives that have sat unused for years - lack of, or solidified lubrication on the rails that the head assembly slides on.

Well, during the initial floppy seek test at POST the head seems to be moving fine. My primary concern is that this drive can not operate as a 1.2MB floppy because it a 720KB floppy drive. As such, it would fail on trying to read a 1.2MB DSHD disk, no?

 

[Chuck(G)]

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.

What you have is 720K (96 tpi, 300 RPM) drive. You can use it by declaring in your BIOS setup that it's a 3.5" 720K drive, but you'll be writing disks that few can read. The 720K format with a 1.2MB floppy is thwarted by the PC BIOS because it double-steps the head to simulate a 360K format (which is why 360K disks formatted or written in a 1.2MB drive often can't be read in a real 360K drive). Further, the PC BIOS expects a 360 RPM drive for the low density mode.

Hope this helps.

 

[Shadow Lord]

Chuck(G), thanks for all the info. So does this mean that my FD55F can write 720KB to DSDD disk (at the cost of not having anyone but myself be able to read them)? Also any idea what the letter R means?

As for:

The 720K format with a 1.2MB floppy is thwarted by the PC BIOS because it double-steps the head to simulate a 360K format (which is why 360K disks formatted or written in a 1.2MB drive often can't be read in a real 360K drive). Further, the PC BIOS expects a 360 RPM drive for the low density mode.

Are you saying that the PC BIOS won't allow me to read/write 720KB disk on a 1.2MB drive unless I specifically call it (in the BIOS) a 3.5" 720KB? So following this logic the only way a FD55GFR could read the disks would also be by changing the BIOS from 1.2MB to 720KB?

Two more question while I have the guru of floppies here :

1. A single speed 1.2MB drives spin at 360 RPM and a dual speed drive will spin at 300 and 360, correct? This results in a slower transfer rate for the 360KB disks but they spin at the correct RPM. So does this increase compatibility? I.E. a 360KB disk that is written to on a 1.2MB drive dual speed drive will continue to be readable on a 360KB drive or will the write spacing of the 1.2MB drive still make the disk unreadable in 360KB drive? If not, then would it be reasonable to say you are better off setting your drive for single speed mode to get faster transfer rates on 360KB disk?

2. Can the FD-55FR correctly read and write a 360KB disk so that it remains usable in a 360KB drive?

Thank you!

 

[MikeS]

You should put this in the form of a quiz ;-)

It is a confusing business, to be sure; I've got my answers written down, waiting to compare them to Chuck's definitive answers...

 

[Shadow Lord]

Trust me Mike,

I went through a bunch of wiki articles and news group archives last night to figure things out. And while I have a whole lot more info today then I did yesterday I am still confused! Add to the fact that most of this info is not available anywhere anymore (try getting some Teac manuals/spec on a fd-55fr drive) and it is almost impossible ot do anting. If I happen to randomly run into scanned/PDF documents here and there I immediately save them just in case... I don't remember it being this complicated back in the day. :huh:

 

[MikeS]

Trust me Mike,

I went through a bunch of wiki articles and news group archives last night to figure things out. And while I have a whole lot more info today then I did yesterday I am still confused! Add to the fact that most of this info is not available anywhere anymore (try getting some Teac manuals/spec on a fd-55fr drive) and it is almost impossible ot do anting. If I happen to randomly run into scanned/PDF documents here and there I immediately save them just in case... I don't remember it being this complicated back in the day. :huh:

Ah, your memory's getting bad then; it was waaaaay more complicated in the days of CP/M and all the other systems where everybody insisted on inventing a new proprietary format.

The PC's variations aren't too bad, except for the funny business of reading and writing 300RPM 40T DD disks in a 360RPM 80T HD drive.

As to your drive, it's not compatible with any 5.25 PC format because it's either the wrong speed, TPI or density; as Chuck says, the only way you can use it is to pretend it's a 3.5 DD drive because that happens to be the same speed, TPI and density (just the wrong size, alas).

Of course I could be wrong; after many years of fooling with different drives & formats I still easily get confused. ;-)

 

[tezza]

What you have is 720K (96 tpi, 300 RPM) drive.

These are useful drives in the TRS-80 world where on a Model 1, they would be known as a 80 track, double sided drive. I have a similar type for my System 80.

Tez

 

[Chuck(G)]

Chuck(G), thanks for all the info. So does this mean that my FD55F can write 720KB to DSDD disk (at the cost of not having anyone but myself be able to read them)? Also any idea what the letter R means?

Right-hand latch, if I remember correctly.

Yes, but be aware that the 55Fs often are jumpered to provide READY on pin 34 instead of DISK CHANGED, so you should make sure that the READY output is disabled.

Are you saying that the PC BIOS won't allow me to read/write 720KB disk on a 1.2MB drive unless I specifically call it (in the BIOS) a 3.5" 720KB? So following this logic the only way a FD55GFR could read the disks would also be by changing the BIOS from 1.2MB to 720KB?

Not even--the 1.2MB drive usually spins at 360 RPM, necessitating a DSDD clock of 300KHz. 3.5" drives and 360K/720K 5.25" drives spin at 300 RPM, using a 250KHz data clock. However, I wrote a driver for 1.2MB drives some time back (well, actually several drivers, but that's another story) that will let you read and write 720K DSDD floppies on a 1.2MB drive.

Of course, you can fiddle with the jumpers on a FD55GF 1.2M drive and get it to operate in dual-speed (300 and 360 RPM) mode and then simply declare it as a 720K drive in your BIOS, but you'll sacrifice the 1.2MB capability.

1. A single speed 1.2MB drives spin at 360 RPM and a dual speed drive will spin at 300 and 360, correct? This results in a slower transfer rate for the 360KB disks but they spin at the correct RPM. So does this increase compatibility?

The compatibility issue has nothing to do with data rate. As I mentioned above, the PC uses either 250KHz or 300KHz for the DD clock, depending on the drive. Some third party controllers (e.g. DTC) could support dual-speed drives, but that's not germane to the compatibility issue.

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.

2. Can the FD-55FR correctly read and write a 360KB disk so that it remains usable in a 360KB drive?

It can read it, of course, assuming that you have a driver that knows to double-step (I've written one of those too). But writing is taboo because of the track-width issue.

Another story...

I was asked many years ago to create ways that a PC user could hide data. I came up with many schemes, among which were the extra sectors on a track, extra tracks, and even encoding data using DDAMs in the format. One I did hid a second 360K floppy on a standard 360K floppy by writing the data on the odd tracks. A normal 5170 with a 1.2MB floppy drive showed no abnormalities. Of course, the floppy was unreadable in a 360K drive, but then, those had lapsed into obsolescence years before...

Thank you!

You're welcome.

 

[tezza]

The PC's variations aren't too bad, except for the funny business of reading and writing 300RPM 40T DD disks in a 360RPM 80T HD drive.

It gets even more amusing when you are trying to do single density! :D

Tez

 

[MikeS]

A single speed 1.2MB drives spin at 360 RPM and a dual speed drive will spin at 300 and 360, correct? This results in a slower transfer rate for the 360KB disks but they spin at the correct RPM. So does this increase compatibility?

If I understand you correctly, no; quite the opposite.

If you set a 1.2MB drive to run at 300RPM then it effectively becomes the same drive as your 55FR and just as incompatible (although you'd have the option of using DD or HD disks ;-) . Right, Chuck?

 

[MikeS]

It gets even more amusing when you are trying to do single density! :D

Tez

And especially when you have both single and double density in different tracks on the same diskette.

And then there are 100TPI drives, and GCR, and ... But we digress!

 

[Chuck(G)]

Exactly. Actually (and this might be fun), you could try declaring it as a 1.44MB drive and seeing if a 1.44MB format would hold on a DSHD floppy. It probably will.

Most of this malarkey stems from the confusion between two "standards"--that for 8" drives (e.g. SA-800) ad that for 5.25" (e.g. SA-400). An 8" drive spins at 360 RPM and records about 250KB on 77 cylinders at 48 tpi, single-sided in FM mode. Micropolis brought out their 5.25" drive that spun at 360 RPM and recorded about 125KB on 77 cylinders at 100 tpi, single-sided FM. But the Micropolis drives initially were fiercely priced--about $600 OEM. Shugart came out with their version of a 5.25" drive by putting 35 tracks at 48 tpi, single-sided, on a disk spinning at 300 RPM for about 90KB FM--and their drives were cheap in comparison--and rather stripped down in comparison to the Micropolis.

Initially, it seemed as if the Shugart standard of 48/96 tpi and 300 RPM won out--everywhere except Japan. There, NEC went from 8" to 5.25" and finally to 3.5", changing nothing about the interface except for the drive. So all formats contain exactly the same amount of data and spin at the same speed (360 RPM). It also explains why just about all 1.2MB drives were Japanese-made, including the ones on the 5170.

 

[Shadow Lord]

Ah, your memory's getting bad then; it was waaaaay more complicated in the days of CP/M and all the other systems where everybody insisted on inventing a new proprietary format.

MikeS my memory isn't getting that bad, it just doesn't go that far back. ;D I got my first XT (True IBM XT) back in 1988. Before then I had a ZX Spectrum that got fed through the home stereo systems tape player. It worked, every once in a while! . I admit I missed alot of fun. By the time I had my first PC things had stabilized a bit. Plus, lack of a budget meant I didn't get to play w/ many cool new toys. So, the XT was minimally upgraded w/ a SVGA card and a Z80 CPU. Things like spindle rates weren't even on my radar since I was trying to figure out how did I destroy the HDD after only two days so it wouldn't boot! Luckily, there was the well bound, three ring binder of PC-DOS 3.30 user's guide! :D But I digress....

 

[Shadow Lord]

It gets even more amusing when you are trying to do single density! :D

Tez

In what way? I have never seen a SD drive in actual use...

 

[Shadow Lord]

If I understand you correctly, no; quite the opposite.

If you set a 1.2MB drive to run at 300RPM then it effectively becomes the same drive as your 55FR and just as incompatible (although you'd have the option of using DD or HD disks ;-) . Right, Chuck?

Hmm... I didn't know the drives could be set to 300 RPM. I thought the options were either dual speed (300/360) or single speed at 360. What I was asking was if the drive is at 300 RPM for a 360KB disk will it be more compatible? But as Chuck(G) pointed out the difference in writing will still make the disk unreadable in a nl 360KB drive.

 

[Shadow Lord]

Right-hand latch, if I remember correctly.
Of course, you can fiddle with the jumpers on a FD55GF 1.2M drive and get it to operate in dual-speed (300 and 360 RPM) mode and then simply declare it as a 720K drive in your BIOS, but you'll sacrifice the 1.2MB capability.

Thats what I thought. Interesting bit about the driver, did it work like the 2M and fdformat programs?

The compatibility issue has nothing to do with data rate. As I mentioned above, the PC uses either 250KHz or 300KHz for the DD clock, depending on the drive. .... 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. ... 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.

Thats pretty much I gleaned from my reading. So short answer is if you need your 360kb disks to remain compatible use a real 360kb drive!

I was asked many years ago to create ways that a PC user could hide data. I came up with many schemes, among which were the extra sectors on a track, extra tracks, and even encoding data using DDAMs in the format. One I did hid a second 360K floppy on a standard 360K floppy by writing the data on the odd tracks. A normal 5170 with a 1.2MB floppy drive showed no abnormalities. Of course, the floppy was unreadable in a 360K drive, but then, those had lapsed into obsolescence years before...

Very Edgar Allen Poe of you Do you still have the program? Or was it a commercial app?

Thanks!



You're welcome.[/QUOTE]

 

[Chuck(G)]

Thats what I thought. Interesting bit about the driver, did it work like the 2M and fdformat programs?

No, I did it the right way--device driver that supports normal FORMAT commands--you just get a different drive letter. I may still have it around. I actually have a raft of floppy drivers that will do things like Eagle 1600, HP-150, DEC Rainbow, etc. floppies. Wonder if the DEC section knows about RAINDOS.SYS?

Very Edgar Allen Poe of you Do you still have the program? Or was it a commercial app?

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.

 

[MikeS]

Hmm... I didn't know the drives could be set to 300 RPM. I thought the options were either dual speed (300/360) or single speed at 360. What I was asking was if the drive is at 300 RPM for a 360KB disk will it be more compatible? But as Chuck(G) pointed out the difference in writing will still make the disk unreadable in a nl 360KB drive.

Well, yes, it would be a dual-speed drive (and many, if not most, 1.2HD drives actually are dual-speed); in a PC they are normally fixed at 360RPM and pin 2 controls the write current, i.e. whether writing a DD or HD disk. Since DD disks are normally read & written at 300RPM with a data rate of 250Kbps, at 360 RPM they are read & written at 300Kbps (360/300 = 300/250), and since the tracks on a 40track DD disk are twice as far apart as the 80 tracks of a HD disk, the HD controller tells the 80T HD drive to take two steps for every step when reading/writing a 40T DD disk. So you can see that if you spin the disk at 300RPM the data will come off the disk at 250Kbps the way it would on a DD drive, but the PC using an HD drive assumes that it's spinning at 360 and expects the data to be coming (and writes it) faster, at 300Kbps; on the disk it looks the same (ignoring the track width issue).

Dual-speed drives usually have jumpers that allow you to either fix the speed at 300RPM (instead of 360) or change the speed along with the write current with pin 2 of the interface; not very useful in a PC, but useful in some other computers like a Toshiba T300 or one of the other ones that originally used your 55FR. So a jumper or two changes the G in a 55GFR to the F, or you can switch back and forth with pin 2.

As a side note, as Chuck sort of mentioned, a 1.2HD drive is effectively equivalent to an 8" drive and they are in fact often used as a replacement; obviously the disks aren't compatible, but the OS doesn't know the difference. Also, there are dual-speed 3.5" drives that can also emulate an 8" drive (and of course also a 1.2HD 5.25 drive).

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.

Hope that I've cleared it up a bit more (and got it right ;-) )