Puzzle: Reading 1988 Mac Floppies

Does the floppy have the "HD" logo on it? If so, it's high-density (1.4 MB). If it's a low-density 800K disk, you might be out of luck. I know the old SuperDrives could read both, but it wouldn't surprise me if newer floppy drives only read high-density. Another possibility is that the disks are corrupt. Floppy disks randomly became corrupt frequently, so do not discount that possibility. If you're still stuck, and desperately need the data on the disks, you could just buy an old Mac on eBay for $20-$30 that would read them.

If you know someone who has an Imation SuperDisk Drive, those can read both 800K and 1.4 MB floppy disks. However, they cannot read 400K floppy disks (which is REALLY annoying). So you'll need to find an old Mac if you have a 400K disk to read.

There's a simple way to identify a 400K disk. If you look at an 800K or 1.4 MB disk, you'll notice that they will have a hole in both the upper left and upper right corners. One is for the disk lock thingy, and the other is to signify it's a higher capacity disk. 400K disks only have 1 hole, for the disk lock thingy -- I don't remember if it's on the left or right, but I think it's on the top right. In any case, it doesn't really matter.

(Funny anecdote: you can actually convert a 400K disk to an 800K disk SIMPLY BY PUNCHING A HOLE IN THE DISK. It sounds counterintuitive that you just have to make a physical hole in the floppy disk, but it works. I believe the reason is that 400K disks are only single-sided, but technology later came that allowed computers to write on both sides, and it didn't require any change in the media. So computers identify the capacity of the disk by this hole.)

Hmm. That's probably not a good sign then. You have high-density 1.4 MB disks, so they should be readable by any floppy drive. I think the disks are probably corrupt.

Double-density are 800k disks. Can be read by G3 Beige and earlier.

High-density are 1.4 MB disks.

Originally posted by MoparShaha
Hmm. That's probably not a good sign then. You have high-density 1.4 MB disks, so they should be readable by any floppy drive. I think the disks are probably corrupt.

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Not every drive can read 1.44 MB disks. The first Apple floppy disk drives capable of reading HD disks was the original SuperDrive. SuperDrives were introduced in 1988 on the Mac IIx. High density floppies are distiinguished from double density floppies by a permanent hole in the case directly opposite the write-protect hole. There was another difference that many people are not aware of. True HD floppies used a magnetic recording medium that was incompatible with the DD medium. However, most floppy disk manufacturers used the same medium for both. Most floppy drives could not detect the difference in media.

Originally posted by GraphicUmp
Double-density are 800k disks.

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Ah yes, totally forgot about that. Sorry for the mistake.

My USB floppy drive won't read 800K disks, only 1.44MB disks.

The 1.44MB disks use MFM like other floppy disks, but the 800K (DSDD) uses a GCR (group-coded recording) specific to Apple. You will have to find an older Mac with a built-in floppy drive to read them.

Another point is that the magnetic fields are very small. Floppy disks are only rated for data retention for 15 years. Beyond that point, the probability is greater than 50% that data errors will render the data unreadable. Your disks are 14 years old - you are on the hairy edge of losing your data.

One of the selling points of ablative WORM was that the disk's data retention was over 50 years. I don't think CD-R has as long a life. Does anyone quote data retention of DVD-Rs?

(edit) If it was the Macintosh Plus, the machine may have had single-sided (400K) drives. Such disks are only readable in very old Macs. I have a Mac Plus. Where are you located?