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Formatting HD disks to 720k

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Mochatea396

Experienced Member
Joined
Feb 9, 2021
Messages
106
Location
Hudson Valley, New York, USA
Greetings fellow enthusiasts,
Can someone explain to me the purpose of putting tape over the second hole on HD 3.5 floppies? I ask because when I format a 1.44 HD disk on one of my Apple ii drives (they are 800k drives) ive never used tape and never had a problem formatting or writing to these disks. And the disks all boot fine in other systems. A friend was telling me unless he puts tape on an HD disk he can’t even get the disk to format on an Apple drive. This is mainly why I’m asking. I understand his disks not formatting without the tape based on how the tape works but why did I not have any problem? What were these disks being formatted to? And all my other drives seem to like the disks it makes. There just is inconsistency between the two of us and I’m trying to clear that up. I have a USB floppy to make disks for my PC and THAT I have to use tape or the PC won’t recognize the disk. Should I start using tape on the HD disks in my Apple drives? I’m becoming a “don’t fix what’s not broken” kind of person lately, and if they work the way I’ve been doing it maybe I’ll just keep it the way that I know works.
Hopefully someone can clear all this up for me.
Thanks
 
Yes, a double density drive won't check for density hole so any 3.5" disk will be formatted as 720K/800K (or other specialized formats of similar capacities). High density drives and their successors like ED (2.88) and floptical drives check for the correct density and won't format to a lower density unless the density holes are covered. Covering the holes if the disk is formatted as 720K/800K ensures that when the disk is placed in a high density drive, the disk is identified as a double density format instead of as a defective 1.44MB disk.

I prefer having disks formatted to the density the disk is designed for but double density formats on high density disks do last long enough to be used in a pinch.
 
The moment you take those Apple II 3.5" disks to a Macintosh with a 1.44mb drive, or a PC 1.44mb floppy drive connected to a device like a Kryoflux, you will need that density hole covered or they will have problems reading the disk.

Personally, I'd cover the density holes in order to prevent any confusion down the road. Even though the Apple II 3.5" drive won't care.
 
There's very little difference in magnetic properties between DD and HD 3.5" floppies. As an interesting aside, I have an old system here that normally takes DD 5.25" disks, but I installed a 3.5" HD drive on it. The data rate is somewhat odd--about 400 bps. I have a large stock of new 3.5" floppies. The DD ones would fail about 2 of 5 times. HD ones with the density aperture taped over never failed.

A sort of reverse problem arises with the older PS/2 systems. To save money, some places formatted them as HD--the drive that IBM used didn't sense the media density. To read those disks on a conventional drive, one adds a hole to indicate HD.
 
I don’t know if anyone else has seen this, but here’s a wacky case I ran into using 1.44mb floppies in a DD drive: for some reason my 512K Macintosh with the original 400K single-sided drive doesn’t seem to properly detect if a disk is inserted unless I put tape over the hole in 1.44MB floppies. Obviously these drives don’t have a density detect function, maybe someone knows if they have an optical sensor or switch coincidentally in the same area or if it’s just some unique spooky quirk to my machine.

But yes, other than this bizarre case DD drives usually don’t care about the hole, the main reason to cover it is if the disk will be exchanged with a machine that *does* care.
 
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