Amiga 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.
https://porterolsen.wordpress.com/2016/06/15/accessing-mac-f... https://c65gs.blogspot.com/2023/10/reading-amiga-disks-in-me....
Microsoft itself was shipping software on ordinary PC floppies formatted for 1.68MB https://en.wikipedia.org/wiki/Distribution_Media_Format
Denise is the video chip. Paula handles interrupts, audio, the floppy data signal (control logic signals are in CIA) as well as the uart.
Management just didn't let their engineers/architects get things done.
Specifically, AmigaOS's floppies write one sector after another, with a single gap in the entire track.
Whereas the IBM PC format has a gap in each sector. This is because RAM was more expensive back then, thus holding an entire track in memory would have an associated cost.
A major factor - I'd argue even more significant than cost of memory - was that the IBM PC used an off-the-shelf floppy disk controller chip (NEC uPDC765A), which was hardwired to support the industry-standard IBM floppy track format (which had evolved from IBM's 3740 mainframe data entry system, introduced in 1973), and didn't support the Amiga's custom track format. Whereas, the Amiga could do this because it didn't actually have a floppy disk controller-the functionality of controlling floppy disks was in part contained in their custom ASICs, and in part implemented in software by the CPU. Unlike the Amiga, the original IBM PC eschewed proprietary ASICs in favour of off-the-shelf chips, in order to minimise time-to-market.
Ironically, it is possible to read arbitrary formats with the debug read track operation. Yet, it needs to find one triple sync word somewhere in the track; a controller limitation.
Unfortunately, the Amiga standard track format didn't account for that, and uses the same sync word (the 4489 one) but double.
It could have been designed to use a different sync word, and include a triple 4489 at the track start, but they didn't think about it at the time.
Some tricks bit-banging the controller allow for writing arbitrary tracks.
It is also possible to read arbitrary tracks, if there's two floppy drives and a standard ibm pc formatted disk is present in the other one, by switching the drive after the controller has started reading.
The track format was designed that way in the early 1970s. RAM was likely one reason for it, but another was that the 3740 used sector gaps as record boundaries; it was commonly configured so each 128 byte disk sector held a single 80-column punch card worth of data. 3740 format floppies support deleting sectors (by using a different sync word in the sector header) so you could delete database records. PC floppy controllers supported deleted sectors too, even though almost no software used them (some copy protection schemes did, but duplicating deleted sectors isn’t hard once you know they exist.) Part of the motivation for 128 byte sectors was likely the fact that it was the smallest power of 2 that could fit a whole punch card.
Also, a whole 3740 track was 3338 bytes (26 sectors of 128 bytes), which was a lot of RAM in 1973; in 1981, a whole PC floppy track was 4096 bytes. 4KB was a lot less expensive in 1981 than in 1973, so by then it would have been less of a motivating factor than when the track format was initially defined.