3-1/2" Floppy Market Cornered

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Thu May 22 15:13:00 2003

> > 2) Even now, HD drives have a switch to detect the hole in the HD disk,
> > and one thing this switch does is to change the head write current to
> > cater for the different coercivity of the DD and HD media.
> >
> > Have you got _proof_ (either from schematics, or by actually measuring
> > the write current in an opertation drive) that the write current is the
> > same for both DD and HD disks in a correctly-functioning name-brand
> > drive? Becasue I am darn sure it isn't!
>
> No, but "DD" drives initially, for obvious reasons, did not have a switch.

True DD drives probably still don't :-).

Incidentally, the Sony drive used in the HP9114 that started this
discussion does have a switch that lines up with the HD-hole. It's used
to detect that a disk has been inserted, and therefore, these drives
don't even recognise an HD disk (they think the drive is empty)

> And, I can easily show you "HD" drives that do not have a switch! IBM did
> not put a switch in their original "1.44" drives in PS/2's. Some users of

How did they work? Did they use the HD write current for all disks? Or
did they use the density select line from the controller, like the 5.25"
1.2M drives do? I would hope the latter.

> those claim that DD diskettes work correctly. (and then later complain
> about the COMPUTER being "unreliable")
>
> At no point has the price differential been so extreme as to justify using
> the wrong diskette on a regular basis. Admittedly, there can be

FWIW, the street price in the UK at the moment is at least a factor of 2
(with the DD being double the price of the HD). This still has not
convinced me to risk my data :-)

> "emergencies", where the correct diskette is unavailable that might result
> in a need to make do with a wrong one.
>

-tony
Received on Thu May 22 2003 - 15:13:00 BST