Drive capacity names (Was: WTB: HP-85 16k RAM Module and HPIB Floppy Drive

Peter Corlett abuse at
Thu Nov 16 05:33:34 CST 2017

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.

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