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The CUDA will be a small button that you press - it will be on the motherboard. It's been so long since I've seen the inside I'm not sure an an 8500.
Here is an Apple Document it talks about CUDA reset.
Also right here is a discussion of how to get to it. It's tough I think on these.
There should be some good info buried on the MacGuru's forums in the Vintage area. I'll search it some and post any relevant information.
All of the Threads here will have talk of the CUDA look for an 8500. Right here might have an 8500.
Here is a Google search with many topics re 8500's and PCI PPC's of that generation.
Good luck, post back any questions. Attached is a drawing of an 8500 mobo the CUDA is in bottom left corner a square looking button.