17 Mar
2002
17 Mar
'02
11:27 a.m.
On Mon, 18 Mar 2002, Tony Duell wrote:
Does any 1.2Mbyte drive do double stepping in
hardware?
Not that I've ever seen.
I've never seen
one that does (in fact most 'double stepping' drives have been modified,
they were not designed like that). And I've just checked the PC/AT BIOS
sources, and that machine most definitely double steps in software when
reading a 360K (40 cylinder) disk in a 1.2M (80 cylinder) drive.
The problem may be occurring (if it exists at all) from programmers trying
to interface with the existing software at too high a level.
One of my "colleagues" (competitors) was trying to do some stuff with DEC
diskettes and reported having problems with it. I never saw his source
code, but since he was trying for emulation with maximum OS transparency,
I'm going to guess that he was trying to use the MS-DOS API "raw
read"/"raw write" routines.
I also got two reports from users of getting (#64) "seek error"s when
trying to read Eagle diskettes in what they said were 1.2M drives. Those
users were unable to provide coherent followup, and had no problems once I
talked them through temporarily installing one of the Eagle drives (QD).
--
Fred Cisin cisin(a)xenosoft.com
XenoSoft http://www.xenosoft.com