Bios get valid hard disks?

[computertrick]

I am trying to make a drive system for my OS but when I check how many drives are ready it says 8 I am using the following code

Code: Select all

...
mov ah, 10h
mov dl, cl
int 13h
cmp ah, 0
je .found
...

Note: the code above is on a loop and CL gets incremented until it reaches 255

I did some testing and found that AH = 0 when a drive is ready is this incorrect? if so does anybody know how I can find out if a drive is in the system or not. And I am emulating with qemu

My reference: http://www.ctyme.com/intr/rb-0631.htm

[AbstractYouShudNow]

If all you want is to know what BIOS drive numbers have an actual corresponding drive, you can:

• Try to read its first sector and check for errors
• Try to read its geometry
• Attempt to verify some of its sectors

I don't remember what exactly, but I think GRUB has a similar way to do this. A valuable reference is http://en.wikipedia.org/wiki/Int_13H