OSDEV Community - Re:looking for optimized asm

Forums

OSDEV Forums

home | post reply | threaded view | help

Boardwalk :: Forum List

Operating System Development Forums

ASM

bradbobak
User

Fresh Osdever

Posts: 1

Karma: 0

looking for optimized asm - 2006/04/13 01:23 Hey guys.. I'm looking for optimized asm code that will take eax holding a linear block and convert to track / head / sector info..
basically in C:

Code:


 
 track = linear / (secs_per_track * num_heads)
 head =  (linear % (secs_per_track * num_heads)) / secs_per_track;
 sector = ((linear % (secs_per_track * num_heads)) % secs_per_track) + 1;

I'm sure this has been done before.. the reason I don't do it myself is that this is going in a 512byte bootsector and I need optimized (read: small) code..
Any help will be appreciated..

| | The administrator has disabled public write access.

OSDEV Community	Advertisement

gaf
User

Platinum Osdever

Posts: 153

Karma: 10

Re:looking for optimized asm - 2006/04/13 08:00 Hello,
if this is meant to be a bootsector for a floppy disk, you can assume standard values for the number of sectors/heads/tracks as disk size and geometry is always the same. By inserting these concrete numbers into your equation the code should get much simpler.

For an example you might have a look at John Fine's bootsector. Read32 in Boot12.asm does exactly what you are looking for..

regards,
gaf

| | The administrator has disabled public write access.

Boardwalk :: Forum List Operating System Development Forums ASM

MamboBoard Forum Component 1.2.2
MamboBoard Components

A WebArticles site. Sponsored by Evoleto. Motorola V525 / Business Directory / Delaware Incorporation / Home Made Bazaar