Here is a set of directions for getting a copy of your bios and modding it. You have to have the card you want modded installed though or you won't be modding the right bios.
Download and install ATItool: http://www.techpowerup.com/atitool/
Click the settings button and choose overclocking in the drop-down menu.
Scroll down until you can see the CONFIG_DIE_FUSES and CONFIG_SUBSTRATE_FUSES.
Verify that your card can be unlocked by checking for an ‘F’ in the indicated positions of the hexadecimal each number. The capital X represents any hexadecimal number (0-9 or A-F).
CONFIG_DIE_FUSES 0xXXXXFXXX
(the fifth character after the little x must be an 'F')
CONFIG_SUBSTRATE_FUSES 0xXXXXXXXF
(the last character must be an 'F')
If ATItool reads an ‘F’ in the indicated spots, you should be able to unlock your card. If not, I am afraid you are out of luck.
Now select miscellaneous in the drop-down menu.
Click the button that says “Save VGA bios to file”. Give the file a simple name like “12pipe.bin”. This will be your backup copy.
Make a second copy, which will be modified, and name it something like “16pipe.bin”.
Download the hex editor from this website (I would recommend using the “stable” version instead of the beta version):
http://www.mh-nexus.de/programs.htm#HxD
This software will allow you to modify your bios to enable the pipelines.
Extract the hex editor program and run it. Open “16pipe.bin”.
Find the row marked 00000070 and the column labeled ‘A’. You should find ‘61’ at that location. The second bit represents the number of disabled pixel pipe quads. Change the data value to ‘60’ to enable all 16 pixel pipes.
Note: If you ever get bord later you can mess around with disabling pipes. 1 means four pipes are disabled (X800GTO), 2 means eight pipes are disabled (X800GT), 3 means twelve pipes are disabled (yep only 4 left active).
Save the modified bios and exit the hex editor.
Flashrom program:
I used ATIflash from the following link:
ATIflash
Include both the original bios file and the modded copy along with the contents of the ATIflash zip on the bootable media.
Now for getting a bootable device when you don't have a floppy drive:
1. Well, you might try this link for a bootable CD:
http://www.nu2.nu/bootcd/#clean
2. If you have a flash drive and can temporarily empty it you might consider that option. I actually tried out making my flash drive DOS bootable and it was easy. I didn't try flashing my bios from it but that should't be any different than from a disk or CD. Here is the link for making a bootable flash drive:
http://www.techpowerup.com/articles/overclocking/vidcard/34/5
You should now be ready to flash, but I'd prefer not to tell you how to do this until you are actually ready. If the process gets messed up, you either need to be able to do it agian blind or you need a PCI graphics card ot use while reflashing the card. I have had this happen to a guy once, but he was able to recover his card.