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Thread View: comp.sys.ibm.pc.programmer
2 messages
2 total messages Started by Hi Ho Silver Sun, 01 Jul 1990 16:08
Re: 1.6 mb diskettes
#875
Author: Hi Ho Silver
Date: Sun, 01 Jul 1990 16:08
51 lines
3184 bytes
$The program uses a "standard" dos format and does not require the user to
$load any sort of "driver" on 90% of IBM compatable hardware out there.
$The 10% of incompatable computers suposidly have "nonstandard bioses" and
$MAXI requires that you load a TSR called smax before it'll work.

   I've used two or three similar programs that all claim to not need a
driver on most machines.  I found it rather interesting that on all the
machines I've tested them on (including some genuine IBM hardware), they
have all refused to work without the driver loaded.  I haven't seen this
particular program, but I'd imagine it works similarly.

$Does anyone know how this program is able to:
$a) squeeze extra space out of any type of disk (i.e. 360k, 720k, 1.2m, 1.44m)
$b) do the above without modification to DOS or using a device driver

   Yup.  Standard diskettes use the following formats:

             360K     720K     1.2M     1.44M
# Tracks      40       80       80       80
# Sectors      9        9       15       18

   What these programs do is increase the number of tracks and/or sectors
on the diskette.  For example, to put 1.44M on a 1.2M diskette, you
simply increase the number of sectors per track to 18.

   The boot sector of any MS-DOS diskette includes such information as:
- the number of bytes per sector
- the number of sectors per cluster
- the number of sectors per track
- the total number of sectors in the volume

   By making appropriate changes to this information, you can tell DOS
how your diskette was formatted.

   One other note:  if you have double-density media (360K or 720K), it
is possible to format these as if they were high-density.  While you will
find a lot of sectors are reported as bad (particularly on the inner
tracks), this will usually provide a diskette with higher-than-normal
storage (typically it provides 800K on a 360K diskette).  But you can't
trust these diskettes; try it with some information you don't need and
you'll find an alarming number of errors.  While I would trust a diskette
formatted with a program like you mention above somewhat more than that,
I still wouldn't use it for any important information, nor would I use
it on more than one system (for reasons including the possibility of
needing a driver, and the minor differences between disk drives that mean
one may read it while another may not).  Just my opinion, though.
-- 
   /Nikebo \ Nikebo says "Nikebo knows how to post.  Just do it."\silver@xrtll/
  /---------\_____________________________________________________\----------/
 /yunexus!xrtll!silver (L, not 1)\ Hi Ho Silver \   just silver for short   /
/Silver:  Ever Searching for SNTF \  Life sucks. \  someone buy me a BEER! /
Re: 1.6 mb diskettes
#884
Author: Chris Petrilli
Date: Sat, 07 Jul 1990 16:29
28 lines
2401 bytes
In article <1990Jul1.160835.19622@xrtll.uucp> silver@xrtll.UUCP (Hi Ho Silver) writes:
>   One other note:  if you have double-density media (360K or 720K), it
>is possible to format these as if they were high-density.  While you will
>find a lot of sectors are reported as bad (particularly on the inner
>tracks), this will usually provide a diskette with higher-than-normal
>storage (typically it provides 800K on a 360K diskette).  But you can't
>trust these diskettes; try it with some information you don't need and
>you'll find an alarming number of errors.  While I would trust a diskette
>formatted with a program like you mention above somewhat more than that,
>I still wouldn't use it for any important information, nor would I use
>it on more than one system (for reasons including the possibility of
>needing a driver, and the minor differences between disk drives that mean
>one may read it while another may not).  Just my opinion, though.

I have found that formatting 360K disks as a quad-density (720K) disk is 
very reliable, and I have backed up many a machine on to these.  Every
time I have treied to use the 1.2M format, it has failed to last any amount
of time (because of the magnetic media), and has never correctly re-formated
to a 360K again after than w/o errors as it did before.   FastBack and many
other backup programs will format 360K disks to 720K in a 1.2M drive and 
it DOES NOT require a driver to use.  It is a standard DOS format that is 
completely understandable.

+ Chris Petrilli                                    "Opinons represented here
| University of Texas at Austin                      do not necessarily
| INTERNET:  petrilli@vondrake.cc.utexas.edu         represent those of a sane
| SNAILMAIL: 429 Brady Lane, Austin, Texas, 78746    person.  Take them as
+ PHONE:     +1 512 327 0986                         simply that."
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