Re: Help needed

From: Martijn van Buul (
Date: 2001-09-03 11:04:36

Ruud Baltissen wrote:
> Hallo allemaal,

Lo Ruud.
> 1) What I need is a conversion from "Track/Head/Sector" to a lineair number.

Exactly what 'type' of THS are you dealing with? Is it a 1541-ish type
of disk (for a diskimage, for example) with a variable number of sectors,
or do you want to convert 'IDE' THS (with a fixed geometry) back and from
a logical block address? (In that case, you may want to use LBA adressing
instead - most disks > 500MB probably support that. No conversion 

> And vica versa of course.
> Information you need:
> HDTRACKL = Low byte number of tracks on harddisk
> HDTRACKH = High byte number of tracks on harddisk
> HDHEADS  = number of heads
> HDSECT   = number of sectors on a track.

It *seems* like you want to have a fixed geometry, in which case it's
reasonably simple:

block(t,h,s)= t * HDHEADS * HDSECT + h * HDSECT + s


block(t,h,s)= (t * HDHEADS + h ) * HDSECT + s

(Saves one multiplication)

THe other way 'round is only slightly more complicated. It is helpful
if you have a 'cylinder'-step.

s = block MOD HDSECT
c = block \ HDSECT

t = c \ HDHEADS

with 'MOD' being the modulo (or the 'remainder' of a division), \ being
an integer division. Ofcourse you can rewrite this to get rid of the MOD
by doing something like

c = block \ HDSECT
s = block - c*HDSECT

t = c \ HDHEADS
h = c - t*HDHEADS

The NRTRACKS is not required at all.

    Martijn van Buul - -
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