Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!sun-barr!newstop!texsun!pollux!attctc!wnp
From: wnp@attctc.DALLAS.TX.US (Wolf Paul)
Newsgroups: comp.sys.ibm.pc
Subject: Re: make your own HD 3 1/2 in floppies
Summary: DoubleDisk works
Message-ID: <8649@attctc.DALLAS.TX.US>
Date: 14 Jul 89 13:58:12 GMT
References: <26260@amdcad.AMD.COM> <8020020@hp-lsd.HP.COM>
Reply-To: wnp@attctc.Dallas.TX.US (Wolf Paul)
Organization: The Unix(R) Connection BBS, Dallas, Tx
Lines: 36

In article <8020020@hp-lsd.HP.COM> russ@hp-lsd.HP.COM (Russell Johnston) writes:
>I saw an ad in PC WORLD (June 1989, page 16) from Biological Engineering, Inc
>for a product called DoubleDisk Converter they claim will allow formatting
>a 'low density' 3.5" diskette to 1.44MB.  They have a money back guarantee,
>and offer to replace any diskette that does not format with a name brand
>high density diskette.  Has anyone tried this product, or know what their
>technique is?  The price is $39.95 + 3.50 shipping (2.40 CA tax), 800/537-4226.

I have their DoubleDisk converter. It is simply a hole punch which holds your
3.5" disk in place so the hole gets put in the right place, opposite the
write-protect hole.

I have found that most of the 720K disks I purchased from MEI Micro work just
fine as 1.44M after punching the hole; the only problems I have seen is
the fact that some of the disks are encased in more brittle plastic than others.
Brittle plastic does not take too kindly to having holes punched in it; it
cracks. But the disks still work, although I would not leave them lying in the
spilt coffee for too long :-)

Alternative propositions I have seen suggest burning a round hole in the disk
with a soldering iron; that should work too, provided the hole is in the right
place. Also, on some 1.44M drives, it is possible to disable the sensor which
distinguishes between the two types of disks. Then you have to use driver.sys
or the equivalent to tell format how to format  the diskettes.

I would be very much interested in a discussion of the magnetic properties
of 360K, 1.2M, 720K and 1.44M diskettes, respectively. Apparently, the
surface difference between double and high density 3.5" diskettes is NOT
THE SAME as the difference between double and high density 5.25" disks.


-- 
Wolf N. Paul * 3387 Sam Rayburn Run * Carrollton TX 75007 * (214) 306-9101
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        NOTICE: As of July 3, 1989, "killer" has become "attctc".