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Odd floppy drive / single dentisty drives and diskettes

L

Luke

Experienced Member
Joined
Apr 3, 2006
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Poland
I bought this floppy drive long time ago and I tought it was regular one mounted in IBM's computers. I think I was asking about this drive some time ago but noone replied.

fddym5.jpg


It's manufactured by Siemens, there's date - 10-1982. I've connected it to PC computer and tried to write some data on DD disc formatted as 160KB (the drive has one read/write head) sometimes I could save and read the data but only few times. I'm pretty sure it isn't PC drive, it has vired height (about 3/4 of full height one). I guess it can be single density drive.

Are such drives and diskettes common?
And what systems used single density?

Luke
 
Luke said:
It's manufactured by Siemens, there's date - 10-1982. I've connected it to PC computer and tried to write some data on DD disc formatted as 160KB (the drive has one read/write head) sometimes I could save and read the data but only few times. I'm pretty sure it isn't PC drive, it has vired height (about 3/4 of full height one). I guess it can be single density drive.
Click to expand...

This appears to be a Siemens FDD-100. A variant of these drives was used in the Osbornes (though not this particular model).

Luke said:
Are such drives and diskettes common?
And what systems used single density?
Click to expand...

Single-density refers to disk formats that store less than 100k of data. No PC ever used them, although PC floppy controllers are supposed to support SD. Because it was not a standard format, many controllers did not implement SD support. That's probably why it doesn't work correctly in your machine.

A number of systems used SD drives, including the Osborne and various other CP/M boxes. The TRS-80 Model I also used them, as well as the Atari 810 drives.
 
The only machine that pops into my head is the Morrow MD-x CP/M boxes, which used those 3/4 high drives. I have a HH drive here with 3/4 high faceplate that came out of a Burroughs external enclosure, but it's DSDD.

--T
 
Fdd-100

Fdd-100

Doesn't single density typically refer to FM recording and double density to MFM ?

The FDD-100's were actually capable of either FM,MFM, IBM System 3740, IBM System 32 formats, depending on what options the were shipped with, and of course the controller.

The drive looks more like a 100-8 than a 100-5 (at least to me) the -5 don't have that big 40-pin pseudo-pal sitting on it.
Here's a link to the 100-5 manual with pictures.
http://www.pestingers.net/PDFs/Disk_drives/FDD100-5_vol1.pdf
patscc
 
patscc said:
Doesn't single density typically refer to FM recording and double density to MFM ?
Click to expand...

Yes, as I understand it the density is not so much related to the drive, but rather the disk controller. I have an old Tandon single sided 40 track drive that writes single density in my System 80 and double density in the Kaypro. It's a matter of what it's attached to.

Tez
 
tezza said:
Yes, as I understand it the density is not so much related to the drive, but rather the disk controller. I have an old Tandon single sided 40 track drive that writes single density in my System 80 and double density in the Kaypro. It's a matter of what it's attached to.
Click to expand...

Exactly. (Legacy) floppy drives (and for that matter "MFM"/ST506/ST412 interface hard drives) are brain-dead. They record what you tell them to, be it FM, MFM, MMFM, GCR, or anything else. Basically, heads write drivers/read amp circuitry, positioner and a spindle motor.

You could probaby record PPM audio on a floppy if the itch struck you.

There are some 8" drives with built-in FM data separators, but those are always optional in their application.
 
Luke said:
And what systems used single density?
Click to expand...

The TRS-80 Model 1 originally did. Many people upgraded to double-density and a more reliable data separation though.

I think the Osborne 1s were originally single density too. (but don't quote me on that).

Tez
 
Sd

Sd

The Osborne 1 did in fact ship with single-density drives.
The original BBC micro comes to mind and the early Atari's had a SS/SD format.
patscc
 
I was able to make photo of drive's head and I've checked, it's one-headed drive.
It's not even similar to FDD-100. It have different sticker on the back - with date and serial number. On the side there is sticker with "MD-Laufwerk" on it. Maybe this could be the model? But I can't find anything about such model on the internet.

 
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