I have to try to remember how to use testbios :-)
I think that you can give it a file which is the vga bios and it will go try to init the card. You can get the vga bios off the card using dumpdevmem on the appropriate flash part.
Let me try to remember some more and I'll get back to you.
We're starting the vga project up again this summer, hope to get further along.
ron