- MCP79 - 9400M
- G96 - 9600M GT (main card, driving the screen)
After setting the G96 to be the main card, on a previous boot, G96's register 0x61c084 will be equal to 0x400 whereas it usually was equal to 0x0, thus leading to a double registration -MCP79's register 0x61c084 is always equal to 0x0.
The NVidia driver always forces POST, which sets G96's 0x61c084 back to 0x0. Setting config=NvForcePost=1 will effectively solve the issue.