1-36
AlphaServer DS20
Service Manual
1.14
Maintenance Bus (I
2
C Bus)
There are two I
2
C buses (referred to as the “I squared C bus”) in this system.
The internal maintenance bus is used to monitor system conditions scanned by
the power control logic on the server feature module, log error state and track
system configuration information. There is a private I
2
C bus between memory
and the C-chip used to provide memory configuration information to the consoles
and operating systems.
Figure 1-19 I
2
C Bus Block Diagram
PK1406-99
Memory
Banks
CPU 0
System
Board
P-Chip 0
OCP
Controller
I C Bus
2
Private
I C Bus
2
I C Bus
Controller
2
XBUS
ISA Bridge
1
up to 4
PCL
Registers
Thermom/
Thermostat
System
Server Feature
Module
C-Chip
NVRAM
