Compaq Portable II - Restoration Problem, Help requested

[Chuck Guzis]

On 1 Jan 2010 at 19:40, Josh Dersch wrote:

> Very interesting, I had no idea.  Looks like Windows 95/98 only:
> http://support.microsoft.com/kb/148637.
> 
> Never heard about this before.  Sounds like a useful idea poorly
> implemented (cue snarky comments).  Recent Windows releases definitely
> don't do this or I'd have had a lot of trouble with my IBM PS/2
> refdisks...

Modern (1.2M 5.25 and 1.44M 3.5) floppy drives come with a "disk 
changed" detection feature (really a "the drive gate was opened--
you'd better check" status).  360K and some 720K drives do not.

Microsoft apparently wanted a volume tracking feature that would work 
for all removable media and so devised the above-described method; 
words in the KB say that the VSN in the boot sector isn't reliable 
enough and the implementors apparently didn't want to take the CP/M 
route of checksumming the first few directory entries of a disk.

One wonders why MS couldn't have picked somewhere else to write if 
they really needed to do it.  We used to warn our customers that if 
they were set on using Win95 to browse floppies to make sure that 
write protect was set on every floppy they looked at--or to disable 
writing  (by clipping the WG* pin on the floppy connector) 
permanently on the floppy drive.

--Chuck