On a sunny day (Sun, 08 Mar 2020 17:11:57 -0000) it happened Daniel James
 wrote in :

>In article , Charlie Gibbs wrote:
>> My first home computer was an 8080 CP/M box with 8-inch floppies.
>> I refused to go to 5 1/4-inch floppies because they had no
>> standard format, making it a pain in the ass to change data with
>> other users.
>
>8" disks weren't that much better -- but at least there was the IBM
>3740 format to fall back on for compatibility. In my first ever job
>(not quite as long ago as yours) we had a Z80 CP/M machine with two
>internal 5.15" floppies and an external 8" drive. That 8" drive
>supported a DS/DD format with a massive 1.3MB capacity.
>
>That machine was lovely to develop on as it had one of the nicest
>keyboards to type on that I've ever encountered ... but it's main
>purpose was as a disk format conversion box -- it could handle dozens
>of formats on both the 5.25" and the 8" drives.
>
>> (This was before the IBM Personal Computer imposed its own standard.)
>
>By the time the IBM PC appeared most CP/M-80 machines I was seeing
>wrote either 10 512-byte or 5 1024-byte sectors on a track on a 5.25"
>floppy -- making 400kB of data in all. The mostly used WD controller
>chips that allowed that. The floppy controller in the PC writes too
>much lead data on each track to achieve that, so the best it can do is
>9 sectors of 512 bytes -- giving 360k (DOS originally wrote only 8
>sectors to keep the addressing simple(r), giving 320k in all).

Not sure you should blame the IBM PC floppy controller,
as I used it in the CP/M clone I wrote, am talking about the 8272 chip.
I used the Kaypro II format with its 40 tracks x 10 sectors, 400kB.
Description of that system here:
 http://panteltje.com/panteltje/z80/system14/system14.doc.txt

Circuit diagram of the floppy controller board I designed:
 http://panteltje.com/panteltje/z80/system14/diagrams/fdc-1.jpg
  IC1 is the 8272, circuit is dated 13-7-1984

Wrote the drivers too of course.


>IBM really screwed up there!

No, maybe it was Microsoft?

My Z80 sytem was faster than the IBM PC when I later added a ram-disk
and on power up loaded a whole 400 kB floppy into that RAM disk,
so no more seek times and read times next zero.
 http://panteltje.com/panteltje/z80/system14/diagrams/index.html

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