[The fundamental components would be the disk drive (either stock or
modified), the controller (possibly heavily modified), and the software]
Hard versus soft sectoring, FM / MFM (single/double denbsity) / GCR are
primarily an issue of controller, although drive hardware can play a part.
For example, Apple ][ used different circuitry on the drive (that was
otherwise basically a Shugart SA400); BUT, Apple ][ diskettes CAN be read
with most "normal" 360K drives using special controllers.
Directory structures (CP/M, TRS-DOS, etc.) are almost entirely a software
issue. Although hardware issues must be resolved first, and controller
can be an issue [how many remember the Data Address Mark issues with
double density on TRS-DOS and derivatives?]
The common sizes of disk drives are:
8"
5.25"
3.5"
There have also been a few others, including:
3" (Amstrad, Canon, earliest Gavilans,Amdek add-on for Aplle and Coco)
3.25" (Dysan bet the copany and lost. Seequa Chameleon 325)
3.9" (IBM. never produced??)
2.5" (Zenith?)
On 5.25" drives, there were a few different intertrack spacings, most
common being
48TPI (tracks per inch)
96TPI (""Quad"" density, and 1.2M "high" density)
There was also a short-lived 100TPI (Micropolis series 2 and Tandon
TM100-4M (M designating 100TPI v the more common 96TPI of 100-4))
Anybody remember the AMLYN drive? capable of variable track spacing, and
had a crude jukebox for swapping 600 Oerstedt (1.2M) diskettes.
3.5" drives are normally 135 TPI, although there were some early 40 track
(Epson Geneva) at 67.5 TPI
8" drives normally ran at 360 RPM.
5.25" drives normally ran at 300 RPM, except for 1.2M, which thought that
it was an 8".
That doesn't REALLY matter, since it can be compensated for by changing
the data transfer rate at the controller.
--
Fred Cisin cisin_at_xenosoft.com
XenoSoft http://www.xenosoft.com
2210 Sixth St. (510) 644-9366
Berkeley, CA 94710-2219
Received on Thu Oct 01 1998 - 20:25:08 BST