SAS Riser Intel® Server System S7000FC4UR TPS
Revision 1.0
Intel order number E18291-001
58
6.2.3 SMBus
The LSI 1078 is not configured as a slave within the boardset SMBus scheme. The SMBus
segment from the system is connected to the SAS riser FRU through the connector. I2C0 port
on the LSI1078 controls all SAS/ROMB related communication on the card. The bootstrap
EEPROM, DDRII DIMM, IBBU, and SES cable connect to this port. A PCA9543 SMB mux is
used to isolate the IBBU and SES cabling header in order to avoid periodic chatter from these
interfaces which would interfere with power-on data retrieval from bootstrap EEPROM.
6.2.4 SAS Riser Power
The main board supplies 12V, 3.3V, and 3.3V_STBY power to the SAS riser. The memory riser
board has on-board regulators to generate 1.5V and 1.8V. The LSI1078* requires 1.5V for core
power and SAS interface. The DDRII interface (both LSI1078* and DDRII DIMM) requires 1.8V.
A switching mechanism is used to change from main 1.8V (S0), Standby (1.8V Stby through
iBBU)(S5), and 1.8V BAT (iBBU in AC OFF). To ensure correct Reset/PWRGD logic out of
PWR FAIL mode, LSI* recommends generating 3.3V from 12V for proper sequencing in select
logic.
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