18 May
2023
18 May
'23
12:25 a.m.
On Wed, May 17, 2023 at 12:02:05PM -0500, Mike Katz via cctalk wrote:
That is because Amiga uses GCR recording rather then
FM or MFM.
Nope. You may have gotten confused with the Commodore 64 drives, which
were very Special, or perhaps early Apple gear.
The Amiga's disk controller supports both GCR and MFM, but MFM was used by
default because it is higher-density and the blitter can be used to perform
MFM decoding. It can read and write PC disks just fine using a third-party
block device driver (one was later bought-in and shipped with Workbench),
but the native format uses a different sector scheme which gets 880kiB on a
DD disk instead of the usual 720kiB of the PC.
Said third-party device drivers are flexible enough that they'll handle
disks from other platforms which use PC-compatible disk controllers such as
the Atari ST, Acorn Archimedes, Sun workstations, and later Apple Macs.
The Amiga pretty much died before HD disks became standard, although some
Amiga-compatible HD drives exist and gave 1760kiB per disk. These were like
hen's teeth even back then. I have one and have never seen another.