Diagnose your computer first. By replace the floppy drive with another 360K drive. Do not use 1.2MB drive. If no change, replace the multi-i/o card or floppy controller.

Cheers,

180 KB is the capacity of single sided double density disks. Are you sure your disks are double sided?

(I have a box of Parrot single sided disks which I bought as a curiosity, as I had never seen single sided disks.)

Logical answer. You know that by now. 180K is half a 360K and how do you do that by cylinders or heads? The logical answer is latter. 😀

By the way, XT can do 720K 3.5" on same XT controller no problem as it can spin same sectors as 180K and 360K do and double the tracks from 40 to 80. Simply boot a later DOS version and use 720K drive instead. Even can use 1.44M drive as 720K drive. More plentiful.

Cheers,

I think the original 1981 IBM PC used 160 KB disks? What were those?

When you just use "format a:" the format program checks the existing disk format and reuses it. It is possible to format a DSDD disk as SSDD. If you add "/u" to the end of your format command (format a: /u) it will ignore the existing format and format them at the full capacity of the drive.

Errius wrote on 2020-04-23, 02:17:

I think the original 1981 IBM PC used 160 KB disks? What were those?

The same. It was just DOS 1.0 that used a format leading to only 160 KB.

maxtherabbit wrote on 2020-04-23, 03:05:

When you just use "format a:" the format program checks the existing disk format and reuses it. It is possible to format a DSDD disk as SSDD. If you add "/u" to the end of your format command (format a: /u) it will ignore the existing format and format them at the full capacity of the drive.

That does not explain why a "format a:" would format it as 180 and then just a reboot later the same "format a:" formats it as 360. If it would just be the fact I have multiple sized floppies that would be a-ok. The issue comes that this weird thing is happening where it formats them as 360 at first but as soon as it goes to 180 it doesn't go back to 360 even if, as I suspect the media is 360.. unless I reboot..

EDIT: I do not need to reboot, just saying "no" to the "do you wish to format another" question and then retyping "format a:" also seems to "reset" the state so he actually checks and goes back to 360 if possible.

Simply use parameters to tell format.com the size of the disks. Unlike with DD and HD, there's no reliable way for the floppy drive to report back to format.com whether a DD disk is SS or DS. Getting random results with the same disk isn't unusual, that's why the /F: parameter is there after all.

https://www.youtube.com/watch?v=77VlOLpWPbk

Errius wrote on 2020-04-23, 13:18:

https://www.youtube.com/watch?v=77VlOLpWPbk

I hope you know that these don't work for PCs (index hole, you can't flip the disk) and have nothing to do with that anyway.

Is there a 'Floppy Disk FAQ' anywhere that explains all of this?

derSammler wrote on 2020-04-23, 11:04:

Simply use parameters to tell format.com the size of the disks. Unlike with DD and HD, there's no reliable way for the floppy drive to report back to format.com whether a DD disk is SS or DS. Getting random results with the same disk isn't unusual, that's why the /F: parameter is there after all.

Problem with this, how do I know what is the right parameter? I have 100's of floppies, no labels on them to tell me anything. I can recognise the 1.2mb ones because there is no "hub ring" but I have no clue how to visually see the difference between a 180 and a 360 floppy.

You can assume that every DD disk you have is a 360KB one. Even those used back then for single-sided floppy drives (Atari, C64, etc.) where 360KB DS, that's why you could format both sides.

If you ever come across a real SS disk, you'll see immediately, because one of the sides has no coating and looks quite different.

derSammler wrote on 2020-04-23, 13:39:

You can assume that every DD disk you have is a 360KB one. Even those used back then for single-sided floppy drives (Atari, C64, etc.) where 360KB DS, that's why you could format both sides.

If you ever come across a real SS disk, you'll see immediately, because one of the sides has no coating and looks quite different.

Thanks! That's good info.

If you don't mind me asking, why do you need hundreds of DSDD and possibly lower capacity DOS-formatted floppies for ?

He probably bought them in bulk on fleabay and wants to test them all before putting data on them.

That reminds me, formatting so many disks - undoubtedly including some bad quality ones with deteriorating media - will make a mess of your drive's heads. The OP should gently wipe the heads with a lint-free cloth or brush to clear off any accumulated residue. Use Iso alcohol and distilled water. Care must be taken however not to knock the heads out of alignment.

You also should inspect each disk before putting it the drive. Turn the media all the way around to make sure there's no dirt or mold. Also make sure there isn't too much friction between the media and the casing - that may damage the drive motor.