Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!unmvax!ogccse!blake!uw-beaver!ubc-cs!van-bc!mdivax1!hiebert
From: hiebert@mdivax1.uucp (Graeme Hiebert)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Low Density Disks in High Densi
Message-ID: <1989Aug25.203723.5972@mdivax1.uucp>
Date: 25 Aug 89 20:37:23 GMT
References: <291@bilver.UUCP> <45900267@uxe.cso.uiuc.edu>
Reply-To: hiebert@mdivax1.uucp (Graeme Hiebert)
Organization: Mobile Data International, Richmond, B.C., Canada
Lines: 37

In article <45900267@uxe.cso.uiuc.edu> coleman@uxe.cso.uiuc.edu writes:
> 
> /* Written  9:13 am  Aug 23, 1989 by bill@bilver.UUCP in uxe.cso.uiuc.edu:comp.sys.ibm.pc */
> /* ---------- "Re: Low Density Disks in High Densi" ---------- */
> >>This raises yet another question: I have a 1.2M 5-1/4" drive in my AT clone.
> >>It is able to read/write low density 360K diskettes (using the 360K format)
> >>with no problems, and I swap 360K diskettes with my XT clone all the time
> >>with no problems. How does the 1.2M drive know to change its write current
> >>in order to successfully write a 360K floppy? 
> 
> >That's simple.  Part of the formatting routine.  You format HD and it goes to
> >the higher current.  DD and it uses the lower.   If the disks had been made
> >different for hd/dd the problems might not exist. 
> /* End of text from uxe.cso.uiuc.edu:comp.sys.ibm.pc */
> 
> That doesn't explain why I am able to successfully read/write 360K diskettes
> FORMATTED WITH A 360K DRIVE in my 1.2M drive! How does the 1.2M drive know not
> to use high write current when writing data to a 360K disk?
> 
> Scott
> kubla@uiuc.edu

I am not the most experienced PC user (indeed, I only used them at a previous
job for 8 months), but it sounds like it would be pretty simple to me.
If the disk requires a high current write, it could specify it
somewhere on the disk when it is formatted.  When it writes data to the
disk, it merely has to first read enough of it to find out what current
it has to use.  Since the 360K disks will not say "use high current,"
the drive uses low current for those disks.  Easy, peasy,
double-squeezy (as my grade 6 teacher used to say).

   -g
-- 
Graeme E. Hiebert                 | So many of us seek pleasures to acquire
hiebert@mdivax1.uucp              | happiness, yet so few of us are happy
...!ubc-cs!van-bc!mdivax1!hiebert | with the pleasures we find.
---------------------------------------------------------------------------