Compaq AlphaServer DS20 Service Manual download pdf (Page 46)

1-36 AlphaServer DS20 Service Manual

1.14

Maintenance Bus (I

C Bus)

There are two I

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

C bus between memory

and the C-chip used to provide memory configuration information to the consoles

and operating systems.

Figure 1-19 I

C Bus Block Diagram

PK1406-99

Memory

Banks

CPU 0

System

Board

P-Chip 0

OCP

Controller

I C Bus

Private

I C Bus

Controller

XBUS

ISA Bridge

up to 4

PCL

Registers

Thermom/

Thermostat

System

Server Feature

Module

C-Chip

NVRAM

1 2 ... 41 42 43 44 45 46 47 48 49 50 51 ... 181 182

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Compaq AlphaServer DS20 Service Manual Page 46