I read/heard/imagined(?) that the reason GPU vendors weren't willing to hand over their source was due to a proportion of their performance being software based. Which then a competitor could also implement.

The other big problem is lawsuit exposure. Given the current state of the patent system it's certain that nVidia drivers infringe on someone's patents.

Closed source drivers make it more difficult for patent owners to check, and launching a lawsuit without evidence of infringement is very expensive.

They claim that their shader compilers/schedulers are part of their performance benefit, yes.

But they don't need to provide that source, just hardware specs. Gallium3d already has shader compilers and schedulers.

But these code bases aren't nearly large enough for it to be a problem for a reasonably sized team armed with decent tools to disassemble and analyze them if the goal is to figure out the techniques used. It might be their reason, but if so it's a damn stupid reason.

So where is my WinModem driver?

You must have misread.

If one has enough info about nvidia hardware in order to make a driver for nvidia hardware, the same info is not enough to make your own nvidia hardware clones.

Sounds like plenty to make drivers for your knockoff hardware, though.

Why would you want to make hardware which is compatible with open source Nvidia drivers?

You sure about that? Read up about ghost-shifts in semiconductor fabs. Bunnie tells a bit of the tale in his story about counterfeit SD cards:

"Very low serial numbers, like very low MAC ID addresses, are a hallmark of the “ghost shift”, i.e. the shift that happens very late at night when a rouge worker enters the factory and runs the production machine off the books"

http://www.bunniestudios.com/blog/?p=918

If you can run the hardware manufacturing off the books, I don't see how access to the driver source code would help. You would just ship the official binaries.

The point was that you don't need to know anything about the driver or hardware to make clones. There are other ways.

Which continues to moot the relevant point: Nvidia are withholding necessary software specs which not only aren't useful in reengineering their hardware, but which fail to protect against fully independent attacks (ghost shift manufacture) which at least allow duplication of current physical product if not producing a superior hardware product.