Bios drive parameters

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PeterS
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Joined: Sat Feb 10, 2007 4:58 am

Bios drive parameters

Post by PeterS »

Hello ! I've got a question about the the returned drive parameter values.
For example for my floppy disk i get following output:

Heads: 1
Cylinders: 79
Sectors: 18

I always thought that floppy disk have 2880 sectors.
1 * 79 * 18 = 1442 sectors.
But if i use
2 Heads * 80 Cylinders * 18 = 2880 sectors.

My question is, why does the function Int 0x13/AH=0x08 output 79 cylinders and 1 head ?

Thanks in advance.
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Brendan
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Re: Bios drive parameters

Post by Brendan »

Hi,
PeterS wrote:For example for my floppy disk i get following output:

Heads: 1
Cylinders: 79
Sectors: 18

I always thought that floppy disk have 2880 sectors.
I would assume it returns maximum valid numbers:

Head numbers: 0 to 1
Cylinder numbers: 0 to 79
Sector numbers: 1 to 18

This is what you'd expect for a normal 1440 KB floppy (and normal values for BIOS functions), and 2 * 80 * 18 = 2880...


Cheers,

Brendan
For all things; perfection is, and will always remain, impossible to achieve in practice. However; by striving for perfection we create things that are as perfect as practically possible. Let the pursuit of perfection be our guide.
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