fdformat tends to work quite well.

What is that?

EDIT: Nevermind - web searches are my friend. Looks like a Linux format program. The only Linux system I have running is my home media server and that computer doesn't have a floppy drive attached to it at all.

https://github.com/christoh/fdformat

The first google hit for me when I type fdformat & dos, second if I only look for fdformat.

edit, I guess this link has the compiled version at the bottom of the page.
https://retrocmp.de/software/fdformat/fdformat.htm

Ok, I'll have a good, long look at those pages. Thank you very much!

http://toastytech.com/files/nformat.html Nformat is the other one, both of them also have the ability to create "strange" formats like Microsoft DMF 21 sector, or to create optimized formats which skew on step so you don't lose a full rotation, typical optimized skew format is 3 for step and 0 or 1 on head switch

There's nothing better than "format a: /u" under DOS.
All you can do is to run format several times - sometimes the media is slightly dirty, and it cleans itself while revolving.
I've seen many times when the first run of format resulted in some bad sectors, the second in fewer bad sectors, and another in no bad sectors at all.

But if this fails, then the hardware is bad, and no software can help.

I use this a lot https://www.softpedia.com/get/System/File-Man … MAXI-Disk.shtml

If you have to start doing that, TBH I'd dispose of them.

Herne data systems maxi disk is helpful on old systems

All floppy disk formatting is low level. If you want the DOS format command to ignore whatever is on the disk, add the /U switch for unconditional

So I've been experimenting with a card marked "CONNER 2MB FLOPPY CONTROLLER"...
I got it to read and write from/to a 1.44 MB floppy connected to that controller, but couldn't do format - "Track 0 bad" error every time, with every diskette.
I don't know wheter the controller is defective, or just lacks this functionality - I got it with a tape drive, and suspect it may be designed especially for tapes.
Nevermind it for now...

The important thing is: I ended up with a few "defective" diskettes...
After going back to a regular FDC, I tried to re-format them using normal DOS "format a: /u", but it ended up with some bad sectors.
Then I went to another PC, running Windows 95 OSR2 with BootGUI=0, and again did "format a: /u" - same amount of bytes in bad sectors, every time!
Couldn't believe they all got damaged...
Formatted once again, this time using DiskDupe...
...no bad sectors at all!

After DiskDupe format, I did "format a: /u" once again - still no bad sectors!
All "defective" diskettes got "repaired", and work just fine.

Looks like "format a: /u" isn't totally unconditional, after all.
It may be a good idea to try with some alternative utility, before throwing out a "bad" floppy...

In my experience, FORMAT /U can't bring back disks with the error Track 0 Invalid Media, but ImageDisk can.

I had many disks that were like that and some others with bad sectors. I use Dave Dunnfield's ImageDisk under DOS and do a few rounds of the Erase Disk command, then go back to FORMAT /U /F:1.44 .. The disks come back to life, and even bad sectors get fixed after a few cycles of back-and-forth between Erase and Format (assuming no physical damage is on the media).

I also start my disk revival process with a media wipe using alcohol soaked microfiber, to rule out the effects of mold and dust on the media. Otherwise you might damage the drive if you keep feeding it dirty/moldy disks.

I think various versions of FORMAT behave differently - but it may also have something to do with differences in hardware and/or BIOS.

Let me repeat myself...

Grzyb wrote on 2021-11-21, 17:36:

I've seen many times when the first run of format resulted in some bad sectors, the second in fewer bad sectors, and another in no bad sectors at all.

...but today, I experienced multiple runs of FORMAT resulting in exactly the same bad sectors count - clearly it didn't even try to re-format the area that was already marked "bad".

If the media is visibly damaged, the situation is clear.
If unusual noise can be heard - like repeated heads recalibration - then there must be something wrong with the media, but there's still some hope it's just dirty.
But if the media looks good, and sounds good, but FORMAT keeps ending up with bad sectors - the problem may be in the software...

Have you tried VGACOPY to format disks? It tries to relocate sectory physically within the track, so you may have success with floppys that show track 0 error.
Have you tried to format disks in a LS120 drive?

I had one or two DD disks back in the day that soft corrupted, I'd stick them in the Amiga, format to Amiga 880K, format back to PC 720k with crossdos on Amiga, then stick them back in the PC can format /U again in DOS and they'd be back to useable. Never had a HD Amiga drive to see if it worked with 1.44 too... but I've since used dd on linux systems for same effect.

edit: DD is double density, dd is a linux util.

I have had an occasion where one drive was misaligned and I got multiple bad floppies on it that actually ended up being a drive issue. One time I had a drive that actually damaged discs due to some caked up gunk on its head...
But as far as super low-level format goes, I use a neodymium magnet stolen from a HDD. It makes even some actually bad floppies work for the duration of getting DOS or windows to install (and then hours later they start begoming unreadable again 🤣)

A few months ago I realigned a floppy drive head by hand. Part of the testing procedure including a full disk write and read. This absolutely put data in all kinds of weird and wrong places on the disk. I can confirm that I had a lot of corruption after the fact, but the disks were recovered just fine with a reformat in another machine. I couldn't use the same drive to format it, because I wasn't sure whether the heads were aligned yet.

Re: If you have a Compaq LTE series laptop with a broken floppy drive, check the belt!