720K v 1.4M (NOT: PC 160K and 320K are NOT SINGLE DENSITY

From: SP <spedraja_at_ono.com>
Date: Sat Dec 27 15:12:14 2003

Good explain !
You could consider to put in like a FAQ ;-)
(not a joke).

But more seriously, I shall check this with one of the old diskettes.

Thanks and Greetings

Sergio

----- Original Message -----
From: "Fred Cisin" <cisin_at_xenosoft.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk_at_classiccmp.org>
Sent: Saturday, December 27, 2003 9:19 PM
Subject: 720K v 1.4M (NOT: PC 160K and 320K are NOT SINGLE DENSITY


> On Sat, 27 Dec 2003, SP wrote:
> > This matter make me think in the problem with the 1.44 Mb floppies
> > we have from 1993 to this date. In that time you could purchase 720k
> > floppies and format it like 1.44Mb floppies without problem. And, even
> > more important, read one 720K floppie formated like one of 1.44Mb.
> > This was valid until the IBM PS VP. This was the last. If I remember
> > it correctly, all the models of floppies of PCs' began to fail in the
> > management of this floppies on this date. Bad matter, because I already
> > have a lot of them with BBS stuff and Clipper libraries from these years
> > that I can access only with one IBM PS/2 70 that I have in the garage.
>
> YOUR problem can be easily repaired with a hole punch and some
> opaque tape.
> What you are describing sounds like an issue of the MEDIA SENSOR.
>
> The original PS/2 drives did not have a sensor. They could not
> tell the difference between a 720K 3.5" and a 1.4M. If you put
> a virgin BLANK diskinto the drive, it would assume 1.4M and
> format it as such, disunirregardless of which kind of disk it
> really was. It would then work marginally OK as that.
>
> Or, you could put a virgin blank 1.4M diskette into the drive,
> and LIE about what it was ("FORMAT A: /T:80/N:9"), and it would
> become a marginally usable 720K diskette.
>
> 720K diskettes were 600 Oersted, and 1.4M were about 720
> to 750 Oersted, so you could take a good 720K diskette and
> turn it into a mediocre 1.4M, or take a good 1.4M diskette
> and make it into a mediocre 720K.
>
> THAT is why they will work with your PS/2 model 70.
>
>
> When other companies got into 1.4M drives, they included a
> "Media Sensor" which could tell which kind of diskette was
> in the drive, by looking for that other hole that is
> symmetrical to the write protect.
> But when you put one of your WRONG diskettes into one of
> those drives, it is sensing what kind of diskette it REALLY
> is, instead of what you are using it as.
> THAT is why they will not work with anything other than your PS/2.
>
>
> Take one of your 1.4M diskettes that you have been using
> as a 720K; put opaque tape over the media ID hole; and
> try it again.
> Take one of the 720K diskettes that you have been using as
> a 1.4M, and punch a hole through it, and try it again.
> Back when 1.4M diskettes cost more than 720K, there were
> commercially available punches sold to suckers and
> cheapskates. Those punches weren't needed for cheapskates using PS/2s.
>
>
> Modern machines WILL still handle 720K.
> Even Windoze XP WILL still handle 720K!
> But the FORMAT options are no longer documented.
> /F:2 no longer works.
> /F:720 no longer works.
> but, /T:80/N:9 DOES still work!
> [Confirmed on current Compaq machines. YMMV]
>
> --
> Grumpy Ol' Fred cisin_at_xenosoft.com
Received on Sat Dec 27 2003 - 15:12:14 GMT

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:35:51 BST