[tom_]

Feels slightly surprising, at least from the comfort of my 21st century armchair, that they went to all that effort for 800 KB per disk. The Atari ST (with an off the shelf 1772 FDC) had no problem with 800 KB - 2 sides, 80 tracks, 10 sectors per track, 512 bytes per sector - and that seemed perfectly reliable.

The Amiga did its own thing, same as the Mac, but at least it got some extra storage. 880 KB per disk!

(880 KB was also an option on the ST, but only for disks written a track at a time, which was impossible to guarantee if using the OS. With 11 sectors per track, writing individual sectors wasn't reliable as the gaps between them are so small. The OS didn't support irregular disk geometry so you couldn't have more sectors on the outer tracks.)

[thought_alarm]

It's all just an evolution of their existing disk drive technology that started well before the last-minute decision to go with the Sony 3.5" drive.

The variable drive speed comes of the development of the "Twiggy" drive, which was an 850 kB 5.25 disk format originally intended for the Apple III in 1980 but never worked reliably.

BTW, the Atari ST uses the same floppy disk format as the IBM PC, 360 kB per side.

The Amiga uses a variable drive speed like the Mac, but they eke out extra capacity by eliminating sectors. This allows an extra 512 bytes per track, but the trade off is that the disk controller can only read or write an entire track at a time, rather than individual sectors.

An infamous Apple II copy protection scheme used the same trick to expand 5.25 disk capacity from 16 sectors to 18 sectors (512 bytes per track).

[rasz]

>Amiga uses a variable drive speed

Amiga uses standard PC drives with slight tweaked pinout https://linuxjedi.co.uk/2020/12/05/converting-a-pc-floppy-dr...

[s800]

The Amiga is fixed RPM or CAV, not CLV like the og Mac. With one exception- later models could halve the RPM to read/write HD floppies (1.44MB PC or 1.76MB Amiga).

[tom_]

360 KB/side was indeed the default for the Atari ST, but there were numerous tools (I think Fastcopy III was the one I usually used) to format with more sectors per track, and 10 sectors/track (so 400 KB/side) was the standard recommendation if you just wanted more data per disk and no hassle. More than 80 tracks was also an option, and 81 or 82 tracks was apparently also reliable. That never sat right with me though, so I didn't do it.

(18 sectors per track with 256 byte sectors is also possible with the 1770 series. This was one of the disk format options on the BBC Micro. Definitely not written a track at a time! There just wasn't the memory for that.)

[ForOldHack]

You only read the data sheets. The twiggy drives had 4 heads to cut latency and had two access windows one in the back like all 5.25 and one in the front for the extra heads. The Lisa used this too.

[brudgers]

Per Wikipedia, early ST's floppies were 360K even though it came out a year after the Macintosh. https://en.wikipedia.org/wiki/Atari_ST#Floppy_drive

Hardware got better really quickly in the 1980's and 90's, including floppy disks. By the end of the 20th century, there were 120MB floppies. Basically Moore's Law seemed to apply to spinning rust for awhile.

[chuckadams]

> By the end of the 20th century, there were 120MB floppies

In the form of Zip disks, yes. I’m reasonably sure 3.5” disks, the last thing to be called “floppies”, topped out at 2.88M.

[wtallis]

LS-120 drives were floptical drives that were backwards-compatible with 3.5" 1.44MB disks. IIRC you needed special media to use the 120MB capacity, but the same slot could accept the common 1.44MB disks and give you much better performance than normal floppy drives. The successor LS-240 drives also had the ability to write 32MB to a standard floppy disk using shingled magnetic recording.

If Zip disks, CD-R and USB flash drives hadn't showed up, these drives would have been pretty widely recognized as the next generation of floppies.

[chuckadams]

Right, I forgot about flopticals… but I guess almost everyone else did too. NeXT boxes had those, didn’t they?

[brudgers]

Almost all digital formats die in obscurity. 3” floppies, 5v SmartMedia, Jazz disks, and DAT were good ideas in the moment that were not good ideas a moment later. The logistics of reading even popular formats like Qic 40 and ADAT today are hard.

[NikkiA]

The most ironic thing, IMO, is that at the time everyone seemed to be holding their breath for Castlewood's 'Orb drive', which promised the perfection of a fast and big storage media.

It was delayed so long that by the time it actually reached the market it didn't get noticed.

[wazoox]

Nope, NeXT had magneto-optical 128 MB drives, somewhat related. They were 3.5" but using an entirely different media, and were absolutely incompatible with ordinary floppies.

[ForOldHack]

NeXT cubes used a 256 Mb optial drive, and some slabs has. 128Mb optical, and someone said that the turbo color slab had a 230Mb optical drive. Mine did not.

[wtallis]

NeXT boxes used magneto-optical disks, which usually meant a laser was used to heat the magnetic material during the write process, and at lower intensity to read data optically. The optics in a floptical drive are just part of the head alignment servo mechanism, so it was probably much easier to make them cheap and backwards-compatible with mainstream floppies.

[rasz]

Op meant LS120.

"Ordinary" floppies peaked in 1988 (yes, before IBM 1990 PS/2 2.88 ED) with 'Triple' or '2TD' format developed and shipped by NEC inside PC-88 VA3. 13MB unformatted, _9,120 kB_ formatted capacity. Triple because it tripled track density from 80 to 240 while reusing ED barium ferrite magnetic media and perpendicular recording head of ED drive, same ~100KB/s speed.

https://necretro.org/PC-88_VA3

https://en.wikipedia.org/wiki/List_of_floppy_disk_formats#:~...

[NikkiA]

There was also the Sony HiFD Which was 200MB and used the same form factor disks as FDHD drives, thus maintaining compatibility.

It had a 'click of death'-like failure like Zip did though, and lost the battle during its recall and redesign. (IOMEGA were lucky in that the click of death didn't really kill Zip's market until about the time that CDR/CDRW was beating them anyway)

[sumtechguy]

With some PC drives you could push the cylinders and sectors and get the same size. There were a couple of utilities out there to do it. However, not all PC drives were alike. So you could do that on your machine and your buddies machine would not read it at all.