NAME
iwm, fd —
floppy disk driver for IWM and non-DMA
SWIM controllers
SYNOPSIS
iwm0 at obio?
fd* at iwm0 drive ?
DESCRIPTION
Theiwm driver interfaces to the built-in and external
floppy disk drives on the Macintosh. It supports double-density media, written
in Apple's proprietary GCR format. Currently, there is no disklabel support
for the floppy drives. Instead, the iwm driver sets up
a fake in-core disklabel, using the minor device number to select from the
supported disk formats.
The following formats are supported:
| Partition | Size | sides | tracks | sectors/track |
| a | 800Kb | 2 | 80 | 10 (default) |
| b | 400Kb | 1 | 80 | 10 |
| c | 800Kb | 2 | 80 | 10 |
(The above table describes the logical mapping as implemented by the driver; the physical layout of GCR floppies has 8..12 sectors per track.)
FORMATTING
The iwm driver does currently not support
floppy disk formatting.
SEE ALSO
Apple Computer, Inc.: "Inside Macintosh", Vol III-33f. (Addison-Wesley)
Apple Computer, Inc.: "New Technical Notes DV 17 - Sony Driver"
Neil Parker: "iwmstuff"
HISTORY
The iwm interface first appeared in
NetBSD 1.4.
AUTHORS
Hauke Fath put together the beginnings of the
iwm driver in 1996 from the sparse documentation in
"Inside Macintosh", Neil Parker's "iwmstuff"
documentation for the Apple IIgs and a long, hard look at the .Sony
driver.
BUGS
The FFS code is incapable of dealing with a varying number of sectors per track. We have to fake a mapping and so lose FFS support for hardware parameters like transition times.
The driver only supports an obsolete format.