Floppy drive questions

[pontifex]

We have an old system here that uses 720 KB floppy disks. I think its one of our CNC laser machines.
Newer floppy drives can read these as well as the 1.44 MB, right?

My boss told me to look for a 720 KB floppy drive. I'll have to ask, but I don't see why a newer 1.44 floppy drive wouldn't work.

 

[airhendrix13]

I know mine can, so I would assume they all can, but I woudn't take my word for it.

 

[pontifex]

i asked about using a newer drive and he said they won't work, he already tried one.

he did find soem on ebay so he's checking those out now.

 

[Paperdoc]

My vague recollection is that the 720 KB floppy, a brief precursor to the 1.44 MB, was simply a floppy that used only one side of the disk, but at the same data density and track count, etc. In order to use them, just like any other drive, you first had to format them. And if you check out the options for the old DOS format command, you'll see that there are command-line switches to specify which type of disk you are formatting.

Now, modern disks come pre-formatted to the 1.44 MB layout. Put those into an old 720 KB drive and it can't read a format it does not understand. In fact, the drive lacks the second-side head that the disk's format info (in the MBB) wants to use. So you simply have to format the disk in the 720 KB drive to the 720 KB format, and it should work.

Now, the other way, if you have a formatted 720 KB disk with data and put it into a 1.44MB drive, it should recognize the format info and read it all just fine. Likewise, it should write to that disk, too, restricting itself to the lesser capacity layout by using only one head. that backward compatibility was designed into DOS, and I would hope it still lurks even in current Windows.

 

[pallejr]

One problem you can run into with floppies, is with head alignment. If the floppy is created on a drive with a head that is not i alignment, you cannot read the floppy in other drives (where the head is correctly aligned).

Normal 1.44 drives can read 720 just fine

 

[nineball9]

Both the 720k and 1.44M floppies are double-sided, however the recording density differs. The 720k diskette was marketed as "DD" (Double Density) while the later 1.44M diskette was marketed as "HD" (High Density) or sometimes marked "MF2HD".

As other posters have noted, a 1.44m floppy drive can read and write a 720k diskette; I did this many times back in the early days of DOS. However, a 720k drive can not read a 1.44M diskette.

Standard 720k diskettes have a single punched-out hole while 1.44M diskettes have an additional hole on the upper left side. The physical floppy drive uses a optical detector (or sometimes, a pin switch) to ascertain the floppy's density. Years ago, one could purchase a square-hole punch to turn 720k diskettes in to 1.44M diskettes, but this didn't always work as the magnetic medium was not identical in the two densities.

Are 720k drives still manufactured? (I think the MAC used an 800k diskette!)