2 System Board

Devices on the SM Bus

Devices on the SM Bus

Device

SM Bus Address

 

 

PIIX4 SM Bus Master

10

 

 

Serial EEPROM

A8, AA, AC, AE

 

 

LM75

90

 

 

SDRAM slot 1

A0

 

 

SDRAM slot 2

A2

 

 

SDRAM slot 3

A4

 

 

PLL

D2

 

 

The System Management (SM) bus is used to monitor several of the hardware functions (such as voltage levels, temperature, fan speed, DIMM presence and type) of the system board. It is controlled by the SM bus controller located in the PIIX4 chip.

Serial EEPROM

This is the non-volatile memory which holds the default values for the CMOS memory (in the event of battery failure).

When installing a new system board, the Serial EEPROM will have a blank serial number field. This will be detected automatically by the BIOS, which will then prompt the user for the serial number which is printed on the identification label on the back of the PC Workstation.

The computer uses 4 Kbit of Serial EEPROM implemented within a single 512 K ✕ 8-bit ROM chip. Serial EEPROM is ROM in which one byte at a time can be returned to its unprogrammed state by the application of appropriate electrical signals. In effect, it can be made to behave like very slow, non- volatile RAM. It is used for storing the tatoo string, the serial number, and the parameter settings for the Setup program.

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