Main contents:
describe the Gigaplane centerplane
describe how and why components are hot-pluggable
describe the purpose and function of the Clock+ board
describe the difference in chassis designs from one Enterprise model to another
locate all chassis-mounted components and subassemblies
remove and replace all chassis-mounted components and subassemblies

The following describes the features of the 100-MHz-capable Gigaplane:
1,CPU/memory boards are usually in even-numbered slots in the front of E4500,E5500,E6500

systems
2,I/O boards are usually in odd-numbered slots in the back

The Gigaplane is a packet-switched bus with the following features:
1,256-bit data width
2,out-of-order completion
3,control and address buses are used at the same time as the data bus
4,sun enterprise x000 systems use a clock speed of 83MHz
5,sun enterprise x500 systems use a clock speed of 100MHz

The 16-slot Gigaplane runs at 90 MHz if you use only the first 12 slots nearest the clock+
board. If you use more than 12 slots, the clock must be reduced to 83MHz. there is no

100MHz in the E6500 system

The clock+ board consists of the following subsystems:
console bus
clocks
reset logic
JTAG logic and interface port for factory testing only
centerplane connector signals monitoring

PCM(Power/Cooling Module) power supplies are used in Enterprise 3x00,4x00,5x00,and 6x00 systems. there must be a 300W PCM for every two adjacent boards in the system, because the fans inside the PCM are the only cooling for those boards.This means that if a board is added to the system, there must be an associated PCM.if one is not present, it must be added.
The PCMs:
are hot pluggable
supply cooling for two adjacent boards
operate in redundant current share mode(N+1) with up to :
   8 on the Enterprise 6x00
   4 on the Enterprise 4/5x00
   3 on the Enterprise 3x00

PPS:peripheral power supply

The CPU/Memory+ boards and the I/O+ boards are hot pluggable under certain conditions. If the operating system detects a hardware failure in the board, the software turns off the green status LED on the board. It might also stop the blinking LED as well, depending on the failure
Note:Hot pluggable is not supported on the sun enterprise 250 and sun enterprise 450

The internal bus is SCSI-II(wide) for the internal disk drives, but operates in SCSI-I(narrow) mode for the removable media bays .Each system has at least one CPU/Memory+ board, and at least one I/O interface board for disk and removable media communications. Each system has a clock+ board that synchronizes everything and provides an interface to an ASCII terminal for boot processes and system administration. Each system has multiple power supplies that enable the hot-swap capability. Each system has space for several internal disk drives and the capability to add more