*EDIT* Thanks to the hardwork and risk taking of several members of this board, you can now use premade bios images to simply this process. View the info here http://www.notebookforums.com/showthread.php?t=92401
If you want to do the work by hand, follow the info below.
*DISCLAIMER* This worked for me. This may not work for you. Heed my advice at your own risk.
If you are not comfortable with these instructions, or you do not understand this post or any subsequent posts by other people with instructions, then you have no business trying this. THIS IS HIGHLY EXPERIMENTAL. You can ruin your machine. AGAIN, IF YOU ARE UNSURE, THEN THIS IS NOT FOR YOU.
*For the 6800 Ultra you will have to hand edit the image. Instructions at end of post.
My setup:
i9300
nVidia 6800 Go (379/768)
Video BIOS version 5.41.02.29.A8
ForceWare version 77.72 (latopvideo2go)
nv42 Board - p242h0
The idea:
Use nvflash to read bios. Use nibitor to edit bios. Use nvflash to write new bios.
OR
Use nvflash to write new bios from external source (such as Sager)
Problems:
nvflash requires DOS to run. i don't have a floppy drive. some people have reported that nvflash does not work. DOS requires FAT file system to save bios image.
Solutions:
create a bootable DOS cd with nvflash. create small FAT primary partition.
OR
create a bootable DOS cd with nvflash and DOS drivers for writable media. create FAT writable media.
As you can see, nothing to rough. I'll detail the steps I used.
Procedure:
Download nvflash 5.10 from http://downloads.guru3d.com/download...f76328ba269048
There are newer versions. This just happened to be the version I used. At a later date I'll test newer versions.
Download NiBiTor from http://www.mvktech.net/content/view/1823/
Follow the instructions to make a BART bootable CD at http://www.nu2.nu/bootcd/#cdromsi up to step 3
Place the contents of the nvflash.zip into the 'files' folder as detailed in step 4.
If you are going to try writable media such as a USB memory stick, search the site for instructions on adding drivers. You can also ignore the partition section.
Complete step 5 to create your CD. Use a CD-R. DO NOT USE A CD-RW.
Obtain a copy of Partition Magic. I cannot detail how to do this, but I'm sure you can come up with a copy.
Create a primary FAT partition. I happened to use 7.8Mb that was sitting unallocated and I named it 'e:'.
(If you are going to flash to another bios instead of editing your own, download the rom for that bios and place it in your new partition.)
Restart your computer with your bootable CD in your CD drive.
During the Dell splash, enter the selective boot menu (F12).
Choose CD-ROM.
Choose most compatibility (first option).
Press enter when the CD prompt is displayed.
You get an R:\ prompt. This will be inside the folder containing nvflash.
Type 'nvflash -c'. This will check to see if your EEPROM is supported. Mine verified. If yours does not, proceed at your own risk (if you even can.)
Type 'nvflash -b c:\orig.rom'. It doesn't matter what you named the drive, use 'c:'. This will create a backup of your original bios.
Type 'nvflash -k c:\orig.rom'. This will compare your EEPROM to the image we created. This will verify it wrote correctly.
(If you are flashing to another bios and do not need to edit your own, skip ahead to the last section.)
Reboot into windows.
Open NiBiTor. Resize program
.
File->Open Bios...
Select the 'orig.rom' file we created.
Edit to your heart's content. I recommend sticking with something simple for now, like clock settings.
Definitely be careful changing anything you don't understand or that the program didn't read in correctly. There are probably other programs out there that could be used to edit the bios image.
File->Save Bios...
Save the file as 'new.rom' in the same folder as 'orig.rom'.
Exit NiBiTor.
Reboot into DOS using your bootable CD again.
At the R:\ prompt enter 'nvflash c:\new.rom'. Follow prompts.
(If you are flashing to a new bios that is not for your vendor/chipset, you will get a prompt asking you to continue. Do so at your own risk.)
(You can also use -p to flash to a non-matching vendor/device-id or -u to flash to a non-matching subsystem-id without prompts.)
If anything goes wrong, flash back to orig.rom.
That's it!
*EDIT*
Here are instructions for manually editing your 6800 Ultra bios.
Get a hex editor. I recommend Hex Workshop, which has a fully functional demo. I've also had better luck editing the original file than editing a modded bios.
SET CORE CLOCK
Open 'Tools->Base Converter'
Select data type 'unsigned short'
Select byte order 'intel'
Enter desired core clock speed in whole Mhz (stock would be 450) into 'decimal' box.
Note provided hex value.
Open 'Edit->GoTo'.
Click 'Beginning of File'.
Select 'Hex'.
Enter '0000ebf5' in 'Offset'.
Click 'Go'.
Type provided hex value.
SET MEMORY CLOCK
Open 'Tools->Base Converter'
Select data type 'unsigned short'
Select byte order 'intel'
Enter desired core clock speed in whole Mhz/2 (stock would be 532) into 'decimal' box. MAKE SURE YOU DIVIDE BY 2!!!
Note provided hex value.
Open 'Edit->GoTo'.
Click 'Beginning of File'.
Select 'Hex'.
Enter '0000ebfa' in 'Offset'.
Click 'Go'.
Type provided hex value.
SATISFY CHECKSUM
Go to the very last block of hex values.
Stock value should be 'FF61'.
Open 'Tools->Generate Checksum'.
Select 'Checksum (16 bit).
Click 'Generate'.
Note your 'Checksum/Digest' hex value.
You will need to edit this last block until your 'Checksum/Digest' = C700.
If you understand hex well, this will be easy for you.
If you are like me and only understand hex not very well, it will take some playing around.
*EDIT* Here is a quick way to do it.
1. Open up windows calculator in scientific mode.
2. Do the checksum-16. Note your result.
3. Set calc to hex, enter checksum result. Set calc to decimal. Note converted value of checksum. We'll call this 'a'.
4. If 'a' is greater than 50944, then subtract 50944 from 'a'. If 'a' is less than 50944, then subract 'a' from 50944. This is our difference 'b'.
5. Set calc to hex. Enter the last block of hex in the file (1 block = 2 hex values = 4 digits. e.g. FFFF). Set calc to decimal. Note converted value of block. We'll call this 'c'.
6. If 'a' was greater than 50944, then subtract 'b' from 'c'. If 'a' was less then 50944, then add 'b' to 'c'. Set calc to hex. This is our final result 'd'.
7. Change last block of hex in file to 'd'.
8. Run checksum-16 again to verify C700.
Good Luck!
UPDATE
Here are some preconfigured bios for the 6800 Ultra hosted by RamIt. These were created using the above method by Cornholio.
http://home.comcast.net/~deschampsco...BIOS_STUFF.zip
If you want to do the work by hand, follow the info below.
*DISCLAIMER* This worked for me. This may not work for you. Heed my advice at your own risk.
If you are not comfortable with these instructions, or you do not understand this post or any subsequent posts by other people with instructions, then you have no business trying this. THIS IS HIGHLY EXPERIMENTAL. You can ruin your machine. AGAIN, IF YOU ARE UNSURE, THEN THIS IS NOT FOR YOU.
*For the 6800 Ultra you will have to hand edit the image. Instructions at end of post.
My setup:
i9300
nVidia 6800 Go (379/768)
Video BIOS version 5.41.02.29.A8
ForceWare version 77.72 (latopvideo2go)
nv42 Board - p242h0
The idea:
Use nvflash to read bios. Use nibitor to edit bios. Use nvflash to write new bios.
OR
Use nvflash to write new bios from external source (such as Sager)
Problems:
nvflash requires DOS to run. i don't have a floppy drive. some people have reported that nvflash does not work. DOS requires FAT file system to save bios image.
Solutions:
create a bootable DOS cd with nvflash. create small FAT primary partition.
OR
create a bootable DOS cd with nvflash and DOS drivers for writable media. create FAT writable media.
As you can see, nothing to rough. I'll detail the steps I used.
Procedure:
Download nvflash 5.10 from http://downloads.guru3d.com/download...f76328ba269048
There are newer versions. This just happened to be the version I used. At a later date I'll test newer versions.
Download NiBiTor from http://www.mvktech.net/content/view/1823/
Follow the instructions to make a BART bootable CD at http://www.nu2.nu/bootcd/#cdromsi up to step 3
Place the contents of the nvflash.zip into the 'files' folder as detailed in step 4.
If you are going to try writable media such as a USB memory stick, search the site for instructions on adding drivers. You can also ignore the partition section.
Complete step 5 to create your CD. Use a CD-R. DO NOT USE A CD-RW.
Obtain a copy of Partition Magic. I cannot detail how to do this, but I'm sure you can come up with a copy.
Create a primary FAT partition. I happened to use 7.8Mb that was sitting unallocated and I named it 'e:'.
(If you are going to flash to another bios instead of editing your own, download the rom for that bios and place it in your new partition.)
Restart your computer with your bootable CD in your CD drive.
During the Dell splash, enter the selective boot menu (F12).
Choose CD-ROM.
Choose most compatibility (first option).
Press enter when the CD prompt is displayed.
You get an R:\ prompt. This will be inside the folder containing nvflash.
Type 'nvflash -c'. This will check to see if your EEPROM is supported. Mine verified. If yours does not, proceed at your own risk (if you even can.)
Type 'nvflash -b c:\orig.rom'. It doesn't matter what you named the drive, use 'c:'. This will create a backup of your original bios.
Type 'nvflash -k c:\orig.rom'. This will compare your EEPROM to the image we created. This will verify it wrote correctly.
(If you are flashing to another bios and do not need to edit your own, skip ahead to the last section.)
Reboot into windows.
Open NiBiTor. Resize program
.File->Open Bios...
Select the 'orig.rom' file we created.
Edit to your heart's content. I recommend sticking with something simple for now, like clock settings.
Definitely be careful changing anything you don't understand or that the program didn't read in correctly. There are probably other programs out there that could be used to edit the bios image.
File->Save Bios...
Save the file as 'new.rom' in the same folder as 'orig.rom'.
Exit NiBiTor.
Reboot into DOS using your bootable CD again.
At the R:\ prompt enter 'nvflash c:\new.rom'. Follow prompts.
(If you are flashing to a new bios that is not for your vendor/chipset, you will get a prompt asking you to continue. Do so at your own risk.)
(You can also use -p to flash to a non-matching vendor/device-id or -u to flash to a non-matching subsystem-id without prompts.)
If anything goes wrong, flash back to orig.rom.
That's it!
*EDIT*
Here are instructions for manually editing your 6800 Ultra bios.
Get a hex editor. I recommend Hex Workshop, which has a fully functional demo. I've also had better luck editing the original file than editing a modded bios.
SET CORE CLOCK
Open 'Tools->Base Converter'
Select data type 'unsigned short'
Select byte order 'intel'
Enter desired core clock speed in whole Mhz (stock would be 450) into 'decimal' box.
Note provided hex value.
Open 'Edit->GoTo'.
Click 'Beginning of File'.
Select 'Hex'.
Enter '0000ebf5' in 'Offset'.
Click 'Go'.
Type provided hex value.
SET MEMORY CLOCK
Open 'Tools->Base Converter'
Select data type 'unsigned short'
Select byte order 'intel'
Enter desired core clock speed in whole Mhz/2 (stock would be 532) into 'decimal' box. MAKE SURE YOU DIVIDE BY 2!!!
Note provided hex value.
Open 'Edit->GoTo'.
Click 'Beginning of File'.
Select 'Hex'.
Enter '0000ebfa' in 'Offset'.
Click 'Go'.
Type provided hex value.
SATISFY CHECKSUM
Go to the very last block of hex values.
Stock value should be 'FF61'.
Open 'Tools->Generate Checksum'.
Select 'Checksum (16 bit).
Click 'Generate'.
Note your 'Checksum/Digest' hex value.
You will need to edit this last block until your 'Checksum/Digest' = C700.
If you understand hex well, this will be easy for you.
If you are like me and only understand hex not very well, it will take some playing around.
*EDIT* Here is a quick way to do it.
1. Open up windows calculator in scientific mode.
2. Do the checksum-16. Note your result.
3. Set calc to hex, enter checksum result. Set calc to decimal. Note converted value of checksum. We'll call this 'a'.
4. If 'a' is greater than 50944, then subtract 50944 from 'a'. If 'a' is less than 50944, then subract 'a' from 50944. This is our difference 'b'.
5. Set calc to hex. Enter the last block of hex in the file (1 block = 2 hex values = 4 digits. e.g. FFFF). Set calc to decimal. Note converted value of block. We'll call this 'c'.
6. If 'a' was greater than 50944, then subtract 'b' from 'c'. If 'a' was less then 50944, then add 'b' to 'c'. Set calc to hex. This is our final result 'd'.
7. Change last block of hex in file to 'd'.
8. Run checksum-16 again to verify C700.
Good Luck!
UPDATE
Here are some preconfigured bios for the 6800 Ultra hosted by RamIt. These were created using the above method by Cornholio.
http://home.comcast.net/~deschampsco...BIOS_STUFF.zip
I'll try it once someone else does it first.. I don't want to risk a bad flash 
