26 Jul
2010
26 Jul
'10
3:31 a.m.
On 25 July 2010 19:19, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
The 720K PC disk format is identical at the cylinder
level to the 360K PC
format, it's just that the former has twice as many cylinders. I assume
your archived disks simply store the contents of a 360K disk in cylinders
0-39 of a 720K disk, leaving the other 40 cylinders empty. In which case
anything that can read a clyinder or sector from a 729K disk is
physically capable of reading your archive disk (a floppy drive reads one
track at a time, so it can't know what is going on on the rest of the
disk). whether you have software problems is another matter...
TBH, I don't know. I'm sure you're right, though. I improvised a
solution involving a couple of instances of DRIVER.SYS and DRIVPARM or
something like that to persuade DOS that a 1.4MB drive was actually a
1.2MB drive, I think.
I once received a 1.44M disk which turned out to
contain a 720K iumage
using the first 9 sectors of each track, the other 9 conteined garbage.
This caused a lot of 'fun'... The hardwre could read it, but until I
realised what it was I had difficulty even getting a directory from it.
Ouch!
Wel, there's this PC for a start. It's a
much-hacked PC/AT (8MHz version)
using the origianl motherboard and many of the original expansion cards.
The main changes are a 486 kldugeboard in the 286 socket (so I can run
linux), an earle IDE controller linked to a now-ancient drive, a 1.44M
3.5" floppy (as well as the origianl 1.2M one of course), a patch to the
ROM BIOS to modify the drive parameter tables (2 extra EPROMs and some
address deocnding logic fitted ot the mainboard, kludgewires all over
theplace), and various other piggy-back chip mods to correct timing
problems, add a drive-in-use LED, and so on.
Wow! *Impressed*
A decade and a half ago I was considering trying to do something much
like that with an original IBM PC if I could find one, using a 386sx
board bodged into an XT-286. The idea being to try to make the best,
fastest PC I could that was at heart an actual IBM PC, not a
compatible.
It was only an idea for a project, for a bit of fun, to try to create
an actual IBM PC that could run WfWg 3.11 in 386 mode, or possibly, if
I was very brave, OS/2 2. I specced it up but never did it.
I'm impressed that you managed not only to get such a thing running,
but to be using it still. For any kind of contemporary usage on the
21st-century Web, it must be incredibly slow.
Other 80x86 machines I own include IBM PCs, PC/XTs, a
PC/XT286 and a
PCjr. A couple of other clones I think, then a DEC Rainbow, RM Nimbus,
HP150, HP150-II, HP110, HP Portable+, HP95LX , 100LX and Omnigo 100, a
Sirus (Victo 9000) and doubtless others that I've forgotten about.
:?)
--
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