Re: PCX5900 into Quadro FX1300
There are sites that claim it is possible, but they are wrong. Since at least 2001 the Quadro series use internal bonding options that make it impossible to change a GeForce into a Quadro.
You can relatively easily change a BIOS to make a card report as a Quadro. It's somewhat more difficult to change board straps to identlfy as a Quadro, but unless you have a chip capper (>$1 million USD) You ain't gonna be making your GeForce into a real Quadro.
Imagine a Honda owner placing a nameplate on his car to say V-TEC. Regardless of what shows to the public, the internals of the car are not V-Tec unless you actually change the engine. Same with Quadro.
I used to drive a Heisenberg, but whenever I'd glance at the speedometer, I'd get lost.