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Floppy drive questions....

marc.hull

Experienced Member
Joined
May 26, 2007
Messages
107
Subject is 5.25" 1.2 MB drives....

Are these drives typically/always 80 track ?

If not, will simply changing the speed effectively turn them into 360K drives or is the lowest common denominator 720K ?

I have a feeling that this is not possible but I am not sure and holding out for the long shot.

Thanks

Marc
 
Marc,

It depends. If the model does have a jumper to allow 300rpm rather than 360rpm then they can be used for 720k (and maybe 360 through double stepping depending on software). Many are stuck at 360rpm though so are only high density.

If you haven't come across it already, this might be a useful reference.

http://www.retrotechnology.com/herbs_stuff/drive.html

Tez
 
A 1.2MB will never *be* a 360K drive because the heads are different. A 1.2MB drive's heads write a narrower track than a 360K's heads do.
 
Thanks guys, you have confirmed what I suspected.

Was the 1.2 MB format around for long and was it used heavily ? I have noticed that they seem to be more readily available and generally cheaper than 360K drives but I assume this is a function of desirability at this time rather than sheer numbers ?
 
They were introduced with the IBM AT and were popular with 286 and 386 clones. As they had no problem READING DD 360k drives (to get legacy data off the old 360k disks and onto a hard drive or 1.2 MB disk), the 360k drive soon went out of fashion. Here is New Zealand it's much easier to find HD drives than 360k half-height ones. I also have a couple of 300 RPM 5.25 inch 720k 80 track drives which are even harder to come by.

Tez
 
Actually, I think they had their origin in the Japanese PC community first, where keeping the same format, regardless of media physical size was the goal and the 1.2MB drive was essentially a shrunken 8" drive. I do have at least one 1.2MB drive (Mitsubishi, I think) that's only 1.2M-capable--no low-denssty capability at all.
 
I think most (all?!) of 5.25" 1.2MB drives are capable of writing 720 KB and 360 KB disks. This is done by increasing data transfer rate from 250 bps to 300 bps (and not by decreasing the disk rotation speed from 360 RPM to 300 RPM).

As others mentioned sometimes native 360 KB drives have trouble reading 360 KB disks written by 1.2 MB drives because later have narrower read/write heads.

5.25" 720 KB drives were manufactured as well (e.g. Teac FD-55F) but were pretty rare in PC compatible computers. If I recall correctly some of Soviet ES1841 (IBM XT compatible) computers were shipped with this type of drive.

In late 80's / early 90's it was very popular to format DD (360KB) disks to 720 KB or 800 KB (800.COM anyone?!) because DD disks were much cheaper than HD ones.
 
I think most (all?!) of 5.25" 1.2MB drives are capable of writing 720 KB and 360 KB disks. This is done by increasing data transfer rate from 250 bps to 300 bps (and not by decreasing the disk rotation speed from 360 RPM to 300 RPM).

Actually it seems both tricks were used...first the rotation speed, then the data rate if the following information is correct.
http://www.retrotechnology.com/herbs_stuff/drive.html#12meg

Tez
 
I think most (all?!) of 5.25" 1.2MB drives are capable of writing 720 KB and 360 KB disks. This is done by increasing data transfer rate from 250 bps to 300 bps (and not by decreasing the disk rotation speed from 360 RPM to 300 RPM)..

Have a look at the specs for the YE-Data YD-380, for example. HD only--no DD support. In fact, pin 2 of the drive interface is NC. There are still plenty of these around.

A company called Weltec made a 1.2M drive that shifted the other way. "360/720K" mode spun the spindle at 300 RPM, whle "1.2M" spun it at 180 RPM. The idea was that you could put a high-density drive on a 5150 or 5160 without changing the floppy controller. It wasn't very successful.
 
Actually it seems both tricks were used...first the rotation speed, then the data rate if the following information is correct.
http://www.retrotechnology.com/herbs_stuff/drive.html#12meg

Tez
Yes, changing the speed or the transfer rate has the same effect; however, for the 720kB 'Quad' density changing the speed to 300RPM has the advantage of being a standard configuration (as was 360kB at 300RPM before IBM's HD drive kludge). Many, if not most, HD drives have dual speed motors and quite a few have jumpers to allow automatic speed selection.

And let's not forget about the (mostly) incompatible DD and HD media types...
 
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