Dell POWEREDGE R610 - Manual (Page 35)

Dell
PowerEdge R610 Technical Guide 35
The PowerEdge R610 BIOS accesses the I 2 C through the ICH9 (Intel I/O Controller Hub 9). There are
two multiplexers (MUX) on the ICH9 I 2 C bus.

One MUX (U_ICH_SPD) controls the DIMM SPDs through four split segments

The other MUX (U_ICH_MAIN) controls the clock buffers, TOE, and USB Hub through four split
segments.
BIOS controls both the MUXes through the two select lines using GPIO pins.
The clock chip, USB hub, and the front panel EEPROM device addresses are located on the IOH I
2 C
bus.