7 ms·
> Fun fact! floppy disks actually contain a lot more surface area than 1.44mb. By my calculation, you'll get closer to 1.70mb but a lot of that extra space is e
by wolpoli 3y ago
> Fun fact! floppy disks actually contain a lot more surface area than 1.44mb. By my calculation, you'll get closer to 1.70mb but a lot of that extra space is earmarked for synchronization barriers and sector / track metadata.
This explains the 2M utility that allowed storing about 1.8mb on a floppy disk. It was fun playing with it.
- pgeorgi 3y agohttps://www.os2museum.com/wp/the-xdf-diskette-format/ https://www.os2museum.com/wp/the-xdf-diskette-format/ has tons of details on IBM's contemporary and somewhat similar format.
- retrac 3y agoI think this is a case where a picture is worth a thousand words. This excellent article "Visualizing Commodore 1541 Disk Contents" [1] by Michael Steil about the Commodore 64 disk format, includes visualizations of the magnetic flux as stored on disk. This bit is particularly relevant: https://www.pagetable.com/docs/visualize_1541/sector.png https://www.pagetable.com/docs/visualize_1541/sector.png See the solid bit at the end of the sector, just before the next header? You could squeeze a few more bytes in there, but if the drive motor is just slightly too fast, it'll overwrite the next sector. That's why there's a gap, tolerance for timing variation. Most floppy drive technologies wrote blindly, guessing where they were on the disk based on timing estimates since the controller last saw a sector header. This is also why disks needed to be "formatted". Not just in the sense of writing the file system data structures, but writing out all the sector headers. This had to be done all at once with the same drive, due to those small timing variations. [1] https://www.pagetable.com/?p=1070 https://www.pagetable.com/?p=1070
- examiga500 3y agoAmiga had floppy drives that could read/write 1.76MB on HD disks and 880K on SD floppys. I think this was possible because they could control the speed.
- basementcat 3y agoMac drives had finer control over the motor RPM. Amiga drives read/wrote a track at a time and had no sector gaps. https://porterolsen.wordpress.com/2016/06/15/accessing-mac-formatted-floppy-disks-without-the-kryoflux/ https://porterolsen.wordpress.com/2016/06/15/accessing-mac-f... https://c65gs.blogspot.com/2023/10/reading-amiga-disks-in-mega65.html?m=1#:~:text=The%20following%20are%20details%20about,No%20gaps%20written%20between%20sectors https://c65gs.blogspot.com/2023/10/reading-amiga-disks-in-me....
- rasz 3y agoThe only HD drive ever available for Amiga was sold with some 4000 units - a modded Chinon FZ357A spinning at half rpm because nobody at commodore knew how to update PLL circuit in Denise. 1.76MB capacity was reached by not using standard PC format. Microsoft itself was shipping software on ordinary PC floppies formatted for 1.68MB https://en.wikipedia.org/wiki/Distribution_Media_Format https://en.wikipedia.org/wiki/Distribution_Media_Format
- Cockbrand 3y agoMy A3000 has an HD floppy drive. I was surprised to find that out, as I hadn't been aware that Amigas with these drives existed.
- snvzz 3y agoNot Denise, Paula. Denise is the video chip. Paula handles interrupts, audio, the floppy data signal (control logic signals are in CIA) as well as the uart.
- bcrl 3y agoPaula being the only chip that had absolutely zero changes from the Amiga 1000 to the 4000. That fact alone is a sad example of Commodore's mismanagement of the platform. Well, except for the CIA which traces its lineage even further back to the C64.
- 3y ago
- brk 3y agoI recall it was also not unheard of to have floppy drives that could be incompatible with each other. A drive that was a tad slow might format a disk that would work for itself, and other drive, but that disk might not work in a drive that was a tad too fast (and vice-versa). This wasn't common, just frequently enough to occur so occasionally as to always be baffling, particularly in an office with lots of PCs. Then there were things like Spiradisc (https://en.wikipedia.org/wiki/Spiradisc https://en.wikipedia.org/wiki/Spiradisc), which created incompatibilities by design.
- jacquesm 3y agoThis happened with tape drives too. Head alignment or track alignment a little bit off and you'd start to lose the high pretty quickly.
- shard 3y agoI remember having to realign my Commodore 1541 floppy drive, which involved a lot of banging sounds if I recall.
- 15457345234 3y agoAt high school (in the 1.44mb / w95 era) I encountered a floppy disk that had literally two different filesystems on it depending on what machine you read it in. Not entirely sure how that worked. One machine showed one filesystem, the rest showed another. I guess the alignment on that one particular drive must have been ridiculously far off baseline.
- ggeorgovassilis 3y agoI remember that, too. Got such a floppy from a computer magazine. I think one was for the PC and then other for Amiga or Atari.
- sonicanatidae 3y agoI have a love/hate relationship with the 1541s. Just the absolute worst drives ever released to the public, but it was that or tapes and while most will agree that the 1541 was a slow FDD, waiting 30+ mins to load a tape (don't forget to flip it) was much worse. Then copy protection companies decided that the very best way to CP software was to create unreadable/unwritable sectors and let the drive slam the head against the arrester trying to read it, because they didn't have to replace the drive. That was a you problem.
- Aachen 3y agoA 2M utility allows storing 1.8M? That's not confusing at all!
- rnd0 3y ago>That's not confusing at all! For real! Do they mean 2MB or 2Mb ?
- hinkley 3y agoI don't think I ever got a stable disk above 1.6MB. Which was just enough for a few things but generally not worth it. The motors in the disk drives could be controlled directly, and you could pack the tracks tighter by stepping the motor just a little bit less than you were supposed to. And in theory if you did it right, other disk drives could read it. 'In theory' is carrying a lot there. I tended to find 1.5something to 1.6something worked and anything higher rarely ever did.
- rasz 3y agoMicrosoft had no problem with 1680KB https://en.wikipedia.org/wiki/Distribution_Media_Format https://en.wikipedia.org/wiki/Distribution_Media_Format
- tom_ 3y agoThis is probably only suitable for write-once PC media as the timing would be quite tight for reliably modifying individual sectors in place.
- scoot 3y agoCould you really step less than a standard track? I would have assumed that the stepper motor's steps are track aligned, so either you step, or you don't...
- NegativeLatency 3y agoI’d imagine it’s very hardware specific
- rasz 3y agoNo, no standard Shugart interface compatible floppy allows you to do that.
- scoot 3y agoThanks, yes, the article seems to confirm that: "There are 80 tracks on your average 3.5" floppy drive. You can select a given track by pulsing the STEP pin and combining it with the direction select pin."
- sedatk 3y agoMicrosoft was able to distribute Windows 95 in fewer floppies by creating their own floppy disk format called DMF that used utilized more sectors per track.
- rnd0 3y agoIBM did something similar ...I want to say with OS/2 but that can't be right (or I'd have more issues with it under emulation than I have). Maybe with PC-DOS 2000?
- sedatk 3y agoYou’re right, good memory! Apparently, it was called XDF. http://www.os2museum.com/wp/the-xdf-diskette-format/ http://www.os2museum.com/wp/the-xdf-diskette-format/
- sonicanatidae 3y agoPart of this was the tech, I think. Writing the 1 depends on the precision of the magnets and I suspect they just weren't able to utilize the media better, with the tech of the time. Now we use lasers. ;)
- calamari4065 3y agoBits und Bolts on YouTube did a fantastic breakdown of just how far you can push a floppy disk. https://m.youtube.com/watch?v=qSehRwClXNk https://m.youtube.com/watch?v=qSehRwClXNk Tldr, a bit more than 1.7MB.