13 Sep
2012
13 Sep
'12
2:21 a.m.
On 12 Sep 2012 at 18:51, Fred Cisin wrote:
On Wed, 12 Sep 2012, Chuck Guzis wrote:
Or 10 sectors of 512, but you miss the point, I think. You can't
read or write PC98 disks in a garden-variety PC or Mac floppy drive,
as those aren't usually 3-mode. Before I could get reasonably-priced
3-mode drives, I'd just use a secondary FDC and change the 24 MHz
crystal to 20 MHz. Mohammed to the mountain and all that...
Are you thinking of the Microsoft distribution mode (DMF)? 21
sectors of 512 bytes. Far more interesting was IBM XDF. If memory
serves, 1 sector each of 8192, 2048, 1024 and 512 bytes per track.
That's 11,176 formatted bytes per track, so only 1,326 bytes per
track were used for headers, CRCs, gaps and sync bytes. IBM had a
lot of guts to try something like that as an "official" format.
--Chuck
I think what some are missing is that that 1024
byte sector size was
customarily used with a 360 RPM spindle speed (1.23/1.3 MB 3.5"
format). AKA NEC PC98 format, although it wasn't restricted to NEC
machines.
It wasn't even restricted to the NEC PC98 format.
In "720K" mode (300 RPM, 250K bits per second), you could run 5
sectors of 1024 bytes each, and get 800K per disk.
What was the sector size of the "1.7M" "IMD" distribution formats?