Re: New card PCI Nvidia into my Sun Ultra 5?
It's an uphill battle.
It won't work primarily because OpenBoot won't be able to find a compatible console-emulation ROM on the Nvidia card.
(Typically most Sun-provided graphics cards are just ATI Rage/Radeons or 3DLabs kit but with special ROMs)
Also they haven't bothered with porting the frame buffer driver to SPARC for NVxx series chips.
Now if you managed to somehow cross-compile the fb driver for NV on x86 opensolaris to SPARC, and get it to work, and get Xsun (minus whatever incompatible extensions you run across) to work, you might be able to swing it.
Of course, you still don't get video at boot time unless you want to write some firmware and get out your soldering iron. So its serial console until you start up X, in the best case.