16 Nov
2017
16 Nov
'17
3:33 a.m.
On Wed, Nov 15, 2017 at 09:44:24AM -0800, Fred Cisin via cctalk wrote:
[...]
3.5" MFM "High Density" (sometimes
called "1.44M", due to the most common
formsat being 1.41 Mebibytes, or 1.44 of a unit of 1000*1024 bytes), were
300 RPM at 500,000 bits per second. (1M unformatted per side)
Another oddity for your collection: because the Amiga's floppy controller had a
500kHz maximum clock, they needed custom drives which slowed down to 150RPM
when they detected a "HD" disk.
Given the Amiga did read-modify-write of whole tracks rather than overwriting
individual sectors, the performance of those things was particularly bad.
Mercifully, nobody attemted to bodge a quarter-speed ED drive onto the Amiga.