Sun Microsystems Sun Blade 1000 Service Manual page 298

Sensors on the CPU modules provide temperature data that is read through an
analog-to-digital converter with an I2C interface.
The motherboard contains a socketed I2C EEPROM that contains workstation-
specific information such as the Ethernet address. This EEPROM can be transferred
to a replacement motherboard. Another I2C EEPROM contains system info for a
diagnostic log.
I2C is also used in the Sun Blade 1000 and Sun Blade 2000 workstations for a smart
card reader interface.
Clock Synthesizers
The BBC ASIC supports another serial interface to access the clock synthesizers.
Synthesizers allow frequency margining on the system clock and the UPA64S clock
frequency.
After a power on reset, the clock frequency for the system is set at a default low
frequency (100 MHz). The multiplier in the CPU modules also are set at their lower
value. The OpenBoot PROM software determines the optimal system frequency by
reading the I2C EEPROMs on the module and the motherboard. The OpenBoot
PROM software programs the new multiplier values in the CPU processors and
adjusts the frequency of the synthesizers. A subsequent reset will activate the new
multiplier values inside the processors.
Miscellaneous functions
The BBC also supports the following functions:
Scratch pad memory (2 Kilobytes organized in 256 registers of 64 bits)
Energy Star protocol on the Sun CrossBar Interconnect bus
C-26 Sun Blade 1000 and Sun Blade 2000 Service Manual • January 2002