The wikipedia page is very very detailed, much more so than I need, and I come away from it still wondering about the most commonly used types of these disks. There seems to be 180kb, 360kb, and 1.2mb disks, some of whom are double sided, and I'm not sure if the aforementioned sizes are both sides combined. Can someone give me the lowdown on the types of these and which era they belong to?
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5-1/4 floppy disks
- Thread starter Syntho
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olePigeon
Well-known member
180 KB is single sided, double density (SSDD). 360 KB is double sided, double density (DSDD). 1.2 MB is high density (2HD). There is also the less-common 2.4 MB.
SSDD disks were the first 5.25" floppy disks. They were used in the mid to late 1970s, and likely into the early 1980s. DSDD came about almost immediately after in the late '70s and early '80s. 2HD came about in the early to mid '80s. 2.4 MB disks were mid to late '80s. All of them superseded by the 3.5" micro diskette.
SSDD disks were the first 5.25" floppy disks. They were used in the mid to late 1970s, and likely into the early 1980s. DSDD came about almost immediately after in the late '70s and early '80s. 2HD came about in the early to mid '80s. 2.4 MB disks were mid to late '80s. All of them superseded by the 3.5" micro diskette.
Unknown_K
Well-known member
The 180/360/1.2mb are references to DOS formatted floppies on PC. The same disks used on different systems and under different formats will have different storage space.
A C64 for example uses GCR formatting giving maximum storage capacity of a 5.25" SS-disk is 174,848 bytes, there are as result 683 blocks, of which 664 blocks (approx. 166 Kbyte) are usable for saving. Furthermore a maximum of 144 files can be put on a disk side in the GCR format.
For Apple II: Normal storage capacity per disk side was 114KB with DOS 3.2.1 and earlier (13 256-byte sectors per track, 35 tracks per side), or 140KB with DOS 3.3 and the accompanying firmware update for the controller card (16 sectors/track).
A C64 for example uses GCR formatting giving maximum storage capacity of a 5.25" SS-disk is 174,848 bytes, there are as result 683 blocks, of which 664 blocks (approx. 166 Kbyte) are usable for saving. Furthermore a maximum of 144 files can be put on a disk side in the GCR format.
For Apple II: Normal storage capacity per disk side was 114KB with DOS 3.2.1 and earlier (13 256-byte sectors per track, 35 tracks per side), or 140KB with DOS 3.3 and the accompanying firmware update for the controller card (16 sectors/track).
Franklinstein
Well-known member
Basically you can figure out per-side capacity depending on if the disk is rated for SS or DS operation: take it at face value for SS or halve it for DS disks and that's what you're looking at per side. So if a disk says 180k SSDD, that means it has 180k of storage on its single side. The same disk certified for DSDD operation would have 360k of usable storage (since it's both sides).
3.5" floppies got the same treatment: the original Mac had 400k SSDD floppies while the II and SE came with 800k DSDD floppies. So the same applies: the disks are 400k/side.
If you wanted to, you could use a DS disk in a SS drive (though it's not recommended to go back to DS operation with that same disk because the felt pressure pad in a SS drive can mar the unused surface). And sometimes you can do the opposite: one of the reasons that it was possible for a new generic SS-rated disk (not specifically Apple or Commodore or PC-certified) to be used without issue on a DD drive is that the different manufacturers often disagreed on where to put the heads (top surface for some, bottom surface for others) so each generic/universal disk had to actually be certified on each side so that it could be used reliably on any drive. The SS labels were just there so they could be sold cheaply (and it was also a good way to avoid liability for data loss: the disks technically weren't certified for DS operation so there's no guarantee when they're used as such).
3.5" floppies got the same treatment: the original Mac had 400k SSDD floppies while the II and SE came with 800k DSDD floppies. So the same applies: the disks are 400k/side.
If you wanted to, you could use a DS disk in a SS drive (though it's not recommended to go back to DS operation with that same disk because the felt pressure pad in a SS drive can mar the unused surface). And sometimes you can do the opposite: one of the reasons that it was possible for a new generic SS-rated disk (not specifically Apple or Commodore or PC-certified) to be used without issue on a DD drive is that the different manufacturers often disagreed on where to put the heads (top surface for some, bottom surface for others) so each generic/universal disk had to actually be certified on each side so that it could be used reliably on any drive. The SS labels were just there so they could be sold cheaply (and it was also a good way to avoid liability for data loss: the disks technically weren't certified for DS operation so there's no guarantee when they're used as such).
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