Deja News Toolbar
   
     [INLINE]  Desktops
     [INLINE]  Modems
     [INLINE]  Handhelds [INLINE]  Multimedia
   [INLINE]  Scanners
   [INLINE]  Notebooks [INLINE]  Software
   [INLINE]  Printers
   [INLINE]  Upgrades [LINK] 
   
   message/thread
   
   Message 16 of 100 for search * 
   return to search results help
   
   Re: 5 1/4 hd disks usuable?
   Author:   John Iannetta <73510.2152@CompuServe.COM>
   Date:   1999/03/19
   Forum:   comp.sys.cbm
   
   computerliteracy.comFind books on
   *
   
   more headers author posting history post reply prev next 
   _________________________________________________________________
   
    Matthew Montchalin said,

"Quite true.  OTOH, if the drive could be slowed down a bit so that the r/w
head effectively passed over the surface slower, maybe the reluctance of
the medium could be overcome?  The usual speed of a 5.25 inch drive is 300
rpm, but maybe by replacing the motor (Oh, for goodness' sake, I can see
Cameron slapping his brow on this one) with a slower one, so it only spun at
200 rpm or so, something could successfully be written onto the surface,
and later read back from it?".

    Changing the relative head-disk speed won't give a 1541 the ability to
write to high-density magnetic media.
"Square loop" magnetic material is used; the principal magnetic characteristics
are remnant flux density (Br) and coercive force (Hc).  When writing, the head
must (for a "1") change a magnetic entity (domain) from North-South to
South-North, or the converse.  To do that, current is passed through the head
in the appropriate direction; 5 mA is used for the 1541.  That produces a
magnetomotive force equal to the current, times the number of turns of wire in
the head coil.  The magnetomotive force produces a magnetic field intensity (H)
that must exceed Hc, to "flip" the domain (change from N-S to S-N, or from S-N
to N-S).

    The Hc of double-density material for 5.25" disks is typically 160
oersteds; for high-density material it is 320 oersteds.  The H from the head
will double if you halve the head air gap, or halve the cross-sectional area of
the domain.  But the RPM's of the disk don't enter into the equation.

--
I pressed RETURN, and the message said, "Missing GOSUB".

                          John
   _________________________________________________________________
   
   view for bookmarking
   text only mail this message to a friend
   Sponsored by ComputerLiteracy.com post reply     << prev · next >> 
   subscribe to comp.sys.cbm
   
   SPONSORED LINKS
        Yellow Pages ·  Compare hardware prices! ·  5¢ long distance
    AutoConnect ·  Free Stuff  ·  Trade with Datek  ·  GET IT NOW @ NECX
         FREE downloads! ·  <<Shopping>> ·  Auctions & Classifieds
                                      
                                      
      Home  ·  Communities  ·  My Deja News  ·  Power Search  ·  Post
                                      
              About Deja News  ·  Ad Info  ·  Our Advertisers
            ____________________________________________________
   
   Copyright © 1995-99 Deja News, Inc. All rights reserved.
   Conditions of use  ·  Site privacy statement reviewed by TRUSTe