Text 17404, 57 rader
Skriven 2006-04-12 23:36:00 av MARTIN ATKINS (1:123/140)
     Kommentar till en text av JAY EMRIE
Ärende: Dell WD HD Failure ?
============================
-=> JAY EMRIE wrote to ALAN ZISMAN <=-

 JE> Greetings Alan,
 JE> Thanks for doing the math for me. I have been tied up for a couple
 JE> days. Jay

 AZ>The question is whether 1 kb = 1000 bytes or 1024 bytes, 1 mb = 1000 kb
 AZ>or 1024 kb and 1 gb = 1000 mb or 1024 mb.

 AZ>Even comparing the largest possibility to the smallest, the difference
 AZ>is only 7.4%, not the 18% difference Jay noticed.

Just to add to what Alan was saying. The BIOS limitation occurs because
the early machines could only read up to 1024 cylinders and in some respects
still do. What happens now is that the first 1024 can address another 1024
and the BIOS just sees this as another disk. Then if you have two disks each
one may address another 1024 so the you can expand cylinders of 1024 by 
powers of two.

Computers as you probably know don't think decimal so a real Kb Mb Gb
are a multiples of 1024 x 1024.

1024 x 1024 Kb = 1048576 or 1 Mb
1024 x 1048576 = 1073741824 or 1Gb  

Through smoke and mirrors it's possible to have 1Gig (or more) per group of 
1024 cylinders :)

I did a calculation using my somewhat
rule of thumb method. The 1024 cyls have 1 Gb so :-

cyls
1024 = 1 Gig per cylinders addressed.
2048 = 2
4096 = 4
8192 = 8
16384 = 16
32768 = 32
65536 = 64
131072 = 128

1 gig =   1,073,741,824       so:-
128 gig = 137,438,953,472 bytes

This doesn't mean you can't have an odd number outside the 1024 cyls powers 
of two because your operating system takes control of the MBR on the boot 
disk and reports to the BIOS that any cylinders outside the range are 
just the beginning of another group of cylinders and the BIOS is none 
the wiser.

As has been pointed out by other posters either your BIOS or the operating
system doesn't have the capacity to read all the cylinders. The discrepancy
between the decimal being reported by your machine 132 gig and the 137 it 
should report could be a sign of damage. :(

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