Computer Cousins: The Atari ST and DOS PCs | Hacker News Reader

Computer Cousins: The Atari ST and DOS PCs

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28 pointsrbanffy8 comments

Those of us that used DR-DOS, could make use of ViewMAX, a GEM subset experience.

https://en.wikipedia.org/wiki/ViewMAX

https://www.seasip.info/Gem/History/viewmax1.html

Man this takes me back. We had an Atari ST when we were kids, but it overlapped heavily with the 386 era. But my earliest "what is a computer?" exploration was entirely built around what that machine did when you booted it without a game disk in (and thus got into GEM).

Inspired a feeling I later got when I discovered my grade 5 classroom had an old 286 with Windows 1.0 on it and a really early DOS - just the joy of messing around with old systems.

my st had a 360kb single sided (double density) disk drive.

forgot about the "if you don't format with the pc, the pc won't be able to read it" quirk. takes me back!

hello,

afaik.:

the first model of the ST, the 520 ST - idk if it existed in the "STF"-variant with a build-in floppy-drive - had only a single-sided external drive.

starting with the ST 1040 STF the drive was double-sided - but still single-density :)

just my 0.02€

I think it's even weirder how Sharp/Hudson decided to superficially clone MSDOS for the X68000 independently.

hello,

imho. - as always:

the FDD format was similar to the one of MS-DOS, because they used a hardware floppy-controller from the PC-ecosystem

if i remember it correctly, it was a western digital 177x chip

* https://info-coach.fr/atari/documents/_mydoc/WD1772-JLG.pdf

the data-transfer to PCs was "somewhat" problematic, because the ST used SD - single density - discs with i think ~ 80 tracks, and about 720 k of available storage w/o using any formatting-"tricks".

and the PCs HD floppies hat twice the track-count and around 1,44 m of storage space.

to use HD FDD you had to "double" the step-impulse to the drive to be compatible to the SD drives of the ST.

just my 0.02€

ps. if i remember it correctly, the PC wanted to have some valid checksum in i think the last 2 bytes of the boot-sector ... the ST didn't care much about this!

pps. (commodore) amiga went into the opposite direction, and used some spare i/o ports from their custom sound & graphics-chips to control the floppy ... and implemented the format itself in software => which enabled the amiga to read most of the "foreign" floppy-formats at the time ... [timing hat to be compatible :]

Not quite, the ST floppies were DD (double density). One problem that could occur is that low-end ST configurations - especially the 260ST - were delivered with a single sided floppy drive (SF354, 1 side, 80 tracks, 9 sectors of 512 byte per track, giving 360 kB) instead of a double-sided drive (SF314 with 720 kB).

PC HD floppy drives also have 80 tracks per side, but use twice the data rate (storing 18 sectors of 512 byte each per track) and thus require floppy disks with a different magnetic coating that can handle the higher frequencies. This can also cause problems with data retention and reliability when using 1.44 MB HD disks in DD drives for the ST.

One problem with floppies formatted with early TOS releases (1.0 and 1.02) was that these used a Media Description Byte (offset 0x15) in the boot sector which confuses DOS/Windows system even though the file system format used is FAT12 or FAT16. This was fixed in TOS 1.04.

Details at https://www-user.tu-chemnitz.de/~heha/basteln/PC/usbfloppy/f...

hello,

yes ... you are right, the FDDs were double-density / DD - its been a while :))

cheers

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