based Mac users can mail-order 800K floppy disks from Action. Back to FAQ Index 2.3.3 – Can I use HD floppies in an 800K drive?
While it’s physically possible to do it, those of us with a great deal of experience with Macs almost universally recommend against it. If you absolutely need an 800K disk and only have 1.4MB floppies available, you can force a 1.4MB disk to be an 800K disk by taping over both sides of the hole opposite the write-protect tab. THIS IS ONLY A TEMPORARY SOLUTION. THE DATA ON DISKS FORMATTED LIKE THIS WILL NOT USUALLY SURVIVE FOR LONG. UNDER NO CIRCUMSTANCES SHOULD YOU USE FLOPPIES FORMATTED LIKE THIS FOR STORING DATA LONGER THAN A FEW WEEKS. Don’t say I didn’t warn you… Tom Lee of Stanford has graciously provided the following explanation: To clear up the persistent confusion and superstition about 800K vs. 1.44MB media, here’s the correct story: There is about a ten percent difference in the magnetization thresholds (called “coercivity”) for the two media, with the 800K stuff having the lower value. If you want to get technical, 800K media have a nominal coercivity of 650 oersteds, ver
