http://www.techarp.com/showarticle.aspx?artno=539

I think you should forget about softmodding your 9800GT.

1. The article is a very easy version to follow
2. Your 9800GT is likely to be G92 chip which has no NVstrap shown on Rivatuner anymore. Any possibility to mod the 9800GT will require BIOS flashing. Referring to #1, if you find the article difficult already, you're facing even more trouble on 9800GT.

Top Customize button. First button.

If you don't see NVstrap tab, it is normal. Anything newer than G80 card is likely not to have that option anymore.

You can change Device ID using Nibitor to the Quadro ID which shares similar hardware with 9800GT. For instance, you can try Quadro FX 3700.

Then flash the modified firmware onto the GPU using NVflash.

No one has specifically mentioned that it would work 100%, but it's just something that you can try.

No hardware performance gain.

Only capability to use Quadro drivers which has optimization for 3D rendering software.

Likely to have no effect in games etc.

Do you really happen to use these software?

Quadro does not improve CUDA. Tesla cards, not Quadro, is optimized for CUDA.

I have made BIOS mod on my own Palit 9800GT. I extracted the original ROM, then edited using Nibitor to reflect Quadro FX3700 product ID and flash using NVflash.

Flashing was successful. When the ROM was extracted from the modified GPU EEPROM, it does have the product ID of Quadro FX3700.

BUT. These later generation of Nvidia cards have bootstraps to 'remember' a copy of the factory product ID. GPU-Z and Rivatuner can still identify the card as 9800GT.

Unless someone can help me overwrite the bootstrap, 9800GT doesn't seem to be able to be softmodded to Quadro.

End of story.

I use nvflash. Works for all nvidia card. They do have one variant that can flash in Windows. As long as you can use command prompt, nvflash is the great choice.