This address represents multiple registers (one for each supported function code (FC [3:0] bits (0x66 D [04:01])). The ST [2:0] bits are only reset by power-on. They are used by the BIOS to store configuration information (per AC ’97 Revision 2.3 specifications) and must not be reset by soft, hard or hardware resets. The remaining bits are the result of the last sense operation performed by the impedance sensing circuitry.