flat assembler
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Index > OS Construction > unreal mode

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amitkumartiwari29



Joined: 25 Sep 2005
Posts: 2
Location: India
amitkumartiwari29
can u plz send me the code for unreal mode. I do not know how to avail all the memory of unreal mode. Idea
If possible plz provide the code in C.

Thanx

_________________
How to test that the system is in real flat 4gb mode through a C program.

Please help!
Post 25 Sep 2005, 23:01
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smiddy



Joined: 31 Oct 2004
Posts: 559
smiddy
I'm sorry, I have to laugh, bwa-hahahahahahaha! You want what? C from an assembly forum, are you kidding?

Things you should research:

1) GDT how to setup, the specifics for all permutations of models.
2) How to go to protected mode.
3) How to return from protected mode.
4) How to make certain registers will work with 32-bit memory access.

Sorry, no code, I only know ASM, so I can not provide what I don't have. But, with the knowledge from the above list, you should be able to do it yourself in a short matter of time.

Enjoy your research!
Post 26 Sep 2005, 00:25
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Chewy509



Joined: 19 Jun 2003
Posts: 297
Location: Bris-vegas, Australia
Chewy509
Umm, you do realise that C abstracts the hardware to a point, that the control you are after is not possible? The only way, is to use assembler.

And to quote smiddy: "I'm sorry, I have to laugh, bwa-hahahahahahaha!"

For last years "512 Byte OS Comp" I wrote a machine monitor that ran from the bootsector, but also used unreal mode in it's operation. You can get it here: http://chewy509.atspace.com/256.html . You will need fasm to assemble, and then use one of the many utilities on the Internet to load it onto the first sector of your floppy, (or bootable USB stick, or harddrive). Since it's a bootsector, or just 355 lines of code, it shoudn't be too hard to understand.
Post 26 Sep 2005, 06:00
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