Chapter 2
47
System Board
Hot Bus
Bus Frequencies
There is a 14.318 MHz crystal oscillator on the system board. This frequency is multiplied
to 100 MHz by a phase-locked loop. This is further scaled by an internal clock multiplier
within the processor.
For example, the Pentium III Xeon 400 MHz processor multiplies the 100 MHz system
clock by 4. Switches 2, 3, 4 and 5 set the clock multiplier ratio.
It should be noted that on the HP V
ISUALIZE
Personal Workstations, there are two types of
system board switch boxes. These are shown the section “System Board Switch Boxes” in
this chapter. A table summarizing switches six through to ten is shown in the section
“System Board Switches” in this chapter.
The computer may execute erratically, if at all, or may overheat, or won’t boot if it is
configured to operate at a higher processor speed than the processor is capable of
supporting. This can cause damage to the computer.
If the switches are set to operate at a slower speed than the processor is capable of
supporting, this may also cause erratic behavior in some cases and would reduce the
instruction throughput in others.
Cache Memory
There can be either two integrated circuits (core + 1 cache = 512 KB L2 cache) or three
integrated circuits (core + 2 cache = 1 MB L2 cache) sealed within a single Pentium III
package. One of these contains the Level-2 (L2) cache memory chip; the other contains the
processor, which itself includes Level-1 (L1) cache memory.
The L1 cache memory has a total capacity of 32KB (16 KB data, 16 KB instructions). The
L2 cache memory has a capacity of 512 KB or 1 MB, and is composed of four-way
set-associative static RAM. Data is stored in lines of 32 bytes (256 bits). Thus two
consecutive 128-bit transfers with the main memory are involved in each transaction.
The amount of cache memory is set by Intel at the time of manufacture, and cannot be
changed.
Table 2-5. Switches for Setting the Clock Multiplier Ratio
Processor
Frequency
Switch
1
1. Switches are provided to match the system board to processor frequency when a system
board repair is performed.
Frequency Ratio
Processor:
Local Bus
2
3
4
5
9
400 MHz
OFF
ON
OFF
OFF
ON
4
450 MHz
OFF
ON
OFF
ON
ON
4.5
500 MHz
OFF
ON
ON
OFF
ON
5
550 MHz
OFF
ON
ON
ON
ON
5.5
Summary of Contents for X Class 500/550MHz
Page 6: ...6 Contents ...
Page 8: ...8 Figures ...
Page 15: ...15 1 System Overview ...
Page 66: ...66 Chapter2 System Board Devices on the ISA Bus ...
Page 96: ...96 Chapter3 Interface Boards and Mass Storage Drivers Connectors and Sockets ...
Page 134: ...134 Chapter5 Tests and Error Messages Beep Codes ...
Page 135: ...135 A Regulatory Information and Warranty ...
Page 146: ...146 AppendixA Regulatory Information and Warranty HP Hardware Warranty ...
