So... maybe it is something like a QuadDoubler stuck in a PDS slot instead of the CPU socket, but that raises the other question again: are you *positive* your machine is a 33mhz Quadra 650 instead of a Centris 650? There is almost *no way* a 68040 is going to tolerate an overclock up to 66mhz (remember, even the "50mhz" ones used in the Quad Doubler were actually overclocked 40mhz marked chips) so if that is something like a PDS QuadDoubler it was almost certainly meant for machines like the Quadra 700/900, Centris 610/650, etc. If you run something like Speedometer 4.0 on your system does it correctly identify it as a Q650 and does it benchmark as expected? (Both with and without the card installed?)
(Now I wonder if it's possible, given this has a ROM chip on it unlike the QuadDoubler, if this card is trixy enough to detect if it's plugged into a compatible Mac and disables itself if not?)
