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Emulating the Early Macintosh Floppy Drive

thomasw.dev

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Re: Emulating the Early Macintosh Floppy Drive

#11

Post by tom_ »

thought_alarm wrote: post #7
tom_ wrote: post #3

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…

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 A…

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.)

Re: Emulating the Early Macintosh Floppy Drive

#12

Post by chuckadams »

wtallis wrote: post #10
chuckadams wrote: post #8

Earlier quoted context omitted.

> 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.

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 fl…

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

Re: Emulating the Early Macintosh Floppy Drive

#13

Post by rasz »

chuckadams wrote: post #8
brudgers wrote: post #6

Earlier quoted context omitted.

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.

> 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.

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#:~...

Re: Emulating the Early Macintosh Floppy Drive

#14

Post by rasz »

thought_alarm wrote: post #7
tom_ wrote: post #3

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…

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 A…

>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...

Re: Emulating the Early Macintosh Floppy Drive

#15

Post by wtallis »

chuckadams wrote: post #12
wtallis wrote: post #10

Earlier quoted context omitted.

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 fl…

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

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.

Re: Emulating the Early Macintosh Floppy Drive

#17

Post by wazoox »

chuckadams wrote: post #12
wtallis wrote: post #10

Earlier quoted context omitted.

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 fl…

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

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.

Re: Emulating the Early Macintosh Floppy Drive

#18

Post by Locutus_ »

lisper wrote: post #16

Does anyone make a usb floppy drive capable of reading Mac disks? I would be willing to pay quite a lot for one.

If you have important Mac disks to archive, then a Kryoflux is probably the way to go.

It's a external USB attached floppy drive controller that uses a normal PC floppy drive.

It reads the raw disk stream and software then decodes that for whatever disk format it was. It seems old Mac disks can be recovered with it:

https://www.kryoflux.com/?page=home http://forum.kryoflux.com/viewtopic.php?t=135

Re: Emulating the Early Macintosh Floppy Drive

#19

Post by Lammy »

Locutus_ wrote: post #18
lisper wrote: post #16

Does anyone make a usb floppy drive capable of reading Mac disks? I would be willing to pay quite a lot for one.

If you have important Mac disks to archive, then a Kryoflux is probably the way to go. It's a external USB attached floppy drive controller that uses a normal PC floppy drive. It reads the raw disk stream and software then decodes that for whatever disk format it was. It seems old Mac disks can be recovered with it: https://www.kryoflux.com/?page=home http://forum.kryoflux.com/viewtopic.php?t=135

Also https://github.com/keirf/greaseweazle

Re: Emulating the Early Macintosh Floppy Drive

#20

Post by s800 »

thought_alarm wrote: post #7
tom_ wrote: post #3

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…

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 A…

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).
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