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As someone who didn’t grow up with many floppy disks, how was one able to format a floppy to have a different capacity? I know there’s different “formats” such

As someone who didn’t grow up with many floppy disks, how was one able to format a floppy to have a different capacity? I know there’s different “formats” such as DOS, C64, etc, but I don’t understand why? I have heard about how formatting a floppy involved placing the tracks and how modern hard drives have “hard sectors”, but for some reason, it’s not “computing.”

mytailorisrich 6y ago
Basically your floppy disk is formatted on each side with a number of tracks, each containing a number of sectors of a given size. [1] The standard 720KB 3.5' floppy disk as used by the Atari ST used 80 tracks of 9 sectors. With these tools you could format with, say 11 sectors instead of 9 and boost capacity to 880KB (I think the Amiga was doing that as standard). [1] https://en.wikipedia.org/wiki/List_of_floppy_disk_formats https://en.wikipedia.org/wiki/List_of_floppy_disk_formats
- foobarian 6y ago
  On top of that some tools (I used fdformat) shifted the sectors to speed up sequential reads, i.e. have the first sector of the next track rotate in under the r/w head right as the head arrives. Edit: another unrelated practice was buying up cheap(er) single-density disks, which were distinguished by the lack of a marker hole opposite the r/o protection slider, and used only one side of the medium for data. By drilling it out, one could trick the drives into using both sides, which usually worked out just fine. Mentioned here [1] [1] https://en.wikipedia.org/wiki/Double-sided_disk https://en.wikipedia.org/wiki/Double-sided_disk
  - Zenst 6y ago
    Ah yes, interleaving of the sectors. More prominant with early HD's and using tools like spinwrite to optimise the interleaving. Today it's all 1:1 as processing from the heads just been fast enough for decades to handle the speeds. Spinwrite still exists, though in the early days/versions it was the golden tool for tuning up a system and could make huge differences. Like double your drive speed and more in some instances, but talking late 80's early 90's here when interleaving was thing and mid 90's 1:1 became the norm and made it moot. https://www.grc.com/Spinrite.htm https://www.grc.com/Spinrite.htm
  - 6581 6y ago
    Single-density is not the same as single-sided. There are single-sided double-density disks.
- CWuestefeld 6y ago
  I seem to recall having a program called "Twister" that could format disks like this.
NovemberWhiskey 6y ago
The floppy drive has a stepper motor that controls the placement of the read/write head above the disk. In the ST era, the control of that motor was directly under the control of the operating system. For an 80 track disk, the movement required to step between tracks was a certain known amount. If you formatted the disk with the tracks spaced closer together, by altering the stepper movement during that process, you would 'magically' get more space.
- prox 6y ago
  Weren’t there special compression softwares that added even more capacity?
  - NovemberWhiskey 6y ago
    I don't really remember any: my main recollection as an ST user was the format programs that let you increase the track count and the sector density. I recall the default format was 9 sectors, 80 tracks, 2 sides with 512 bytes per sector = 720KB, and you could push up to sometimes 82/83 tracks and maybe 10 or 11 sectors to get more out of a diskette. Actually, I think my ST originally came with a single-sided floppy drive and had to be upgraded.
    - Zenst 6y ago
      The initial release of Atari's has single sided drives, I think the 1040ST had Double sided though, they did upgrade that shortly afterwards I believe to enable the marketing bods to show a larger number they could compare to the Amiga. So was only early 512STFM systems and those had a red drive light and the double sided had a green one if my memory holds. Sad thing was, due to the early single sided models, many games would limit to 720k so as to not limit there market. That saw games that would happily fit upon a single double sided disc, cast upon two floppies forcing switching. So that small batch of single sided initial release systems, really did have a legacy impact that lasted for years and did it no favours.
  - Zenst 6y ago
    There was, can't recall the one that was popular prior to Microsoft adding https://en.wikipedia.org/wiki/DriveSpace https://en.wikipedia.org/wiki/DriveSpace MSDOS 6.0
Zenst 6y ago
Most discs were rated to format to 80 tracks but some you could format with 81 or 82 and IIRC even 84 on some. Then there was sectors, which was common to have 8, though again you could with better quality discs (quality did get better ahead of the standards) you could go with 9 sectors and higher - https://www-user.tu-chemnitz.de/~heha/basteln/PC/usbfloppy/floppy.chm/ https://www-user.tu-chemnitz.de/~heha/basteln/PC/usbfloppy/f.... Of course, you could think of it as over-clocking - was no guarantee you get that extra capacity, and the early days - it was really luck, but like most things, quality improves and such avenues of formatting became more accessible.

mytailorisrich 6y ago

Basically your floppy disk is formatted on each side with a number of tracks, each containing a number of sectors of a given size. [1] The standard 720KB 3.5' floppy disk as used by the Atari ST used 80 tracks of 9 sectors. With these tools you could format with, say 11 sectors instead of 9 and boost capacity to 880KB (I think the Amiga was doing that as standard). [1] https://en.wikipedia.org/wiki/List_of_floppy_disk_formats https://en.wikipedia.org/wiki/List_of_floppy_disk_formats

foobarian 6y ago
On top of that some tools (I used fdformat) shifted the sectors to speed up sequential reads, i.e. have the first sector of the next track rotate in under the r/w head right as the head arrives. Edit: another unrelated practice was buying up cheap(er) single-density disks, which were distinguished by the lack of a marker hole opposite the r/o protection slider, and used only one side of the medium for data. By drilling it out, one could trick the drives into using both sides, which usually worked out just fine. Mentioned here [1] [1] https://en.wikipedia.org/wiki/Double-sided_disk https://en.wikipedia.org/wiki/Double-sided_disk
- Zenst 6y ago
  Ah yes, interleaving of the sectors. More prominant with early HD's and using tools like spinwrite to optimise the interleaving. Today it's all 1:1 as processing from the heads just been fast enough for decades to handle the speeds. Spinwrite still exists, though in the early days/versions it was the golden tool for tuning up a system and could make huge differences. Like double your drive speed and more in some instances, but talking late 80's early 90's here when interleaving was thing and mid 90's 1:1 became the norm and made it moot. https://www.grc.com/Spinrite.htm https://www.grc.com/Spinrite.htm
- 6581 6y ago
  Single-density is not the same as single-sided. There are single-sided double-density disks.
CWuestefeld 6y ago
I seem to recall having a program called "Twister" that could format disks like this.

NovemberWhiskey 6y ago

The floppy drive has a stepper motor that controls the placement of the read/write head above the disk. In the ST era, the control of that motor was directly under the control of the operating system. For an 80 track disk, the movement required to step between tracks was a certain known amount. If you formatted the disk with the tracks spaced closer together, by altering the stepper movement during that process, you would 'magically' get more space.

prox 6y ago
Weren’t there special compression softwares that added even more capacity?
- NovemberWhiskey 6y ago
  I don't really remember any: my main recollection as an ST user was the format programs that let you increase the track count and the sector density. I recall the default format was 9 sectors, 80 tracks, 2 sides with 512 bytes per sector = 720KB, and you could push up to sometimes 82/83 tracks and maybe 10 or 11 sectors to get more out of a diskette. Actually, I think my ST originally came with a single-sided floppy drive and had to be upgraded.
  - Zenst 6y ago
    The initial release of Atari's has single sided drives, I think the 1040ST had Double sided though, they did upgrade that shortly afterwards I believe to enable the marketing bods to show a larger number they could compare to the Amiga. So was only early 512STFM systems and those had a red drive light and the double sided had a green one if my memory holds. Sad thing was, due to the early single sided models, many games would limit to 720k so as to not limit there market. That saw games that would happily fit upon a single double sided disc, cast upon two floppies forcing switching. So that small batch of single sided initial release systems, really did have a legacy impact that lasted for years and did it no favours.
- Zenst 6y ago
  There was, can't recall the one that was popular prior to Microsoft adding https://en.wikipedia.org/wiki/DriveSpace https://en.wikipedia.org/wiki/DriveSpace MSDOS 6.0

Zenst 6y ago

Most discs were rated to format to 80 tracks but some you could format with 81 or 82 and IIRC even 84 on some. Then there was sectors, which was common to have 8, though again you could with better quality discs (quality did get better ahead of the standards) you could go with 9 sectors and higher - https://www-user.tu-chemnitz.de/~heha/basteln/PC/usbfloppy/floppy.chm/ https://www-user.tu-chemnitz.de/~heha/basteln/PC/usbfloppy/f.... Of course, you could think of it as over-clocking - was no guarantee you get that extra capacity, and the early days - it was really luck, but like most things, quality improves and such avenues of formatting became more accessible.