3System Board (P/Ns D3657-63001 and D3661-63001) Devices on the Processor Local Bus

Switch

 

 

Switch

 

 

 

 

 

 

 

 

 

 

 

 

 

Processor-

 

 

 

Frequency

 

1

2

Local Bus

3

4

7

Ratio

Processor

Frequency

(Processor:

Frequency

 

 

 

 

 

 

 

 

 

 

 

Local Bus)

 

 

 

 

 

 

 

 

 

Open

Closed

66 MHz

Closed

Closed

Closed

2.5

166 MHz

 

 

 

 

 

 

 

 

Closed

Open

60 MHz

Open

Closed

Closed

3.0

180 MHz

 

 

 

 

 

 

 

 

Open

Closed

66 MHz

Open

Closed

Closed

3.0

200 MHz

 

 

 

 

 

 

 

 

The computer will execute erratically, if at all, if the configuration switches are set to operate at a higher processor speed than the processor is capable of supporting. This may cause damage to the PC.

Setting the switches to operate at a slower speed than the processor is capable of supporting would not cause any failure of operation but would cause instructions to be executed more slowly than they should be.

Cache Memory

The PC allows for the provision of two levels of cache memory:

•Level-one cache memory which is fabricated by Intel in the Pentium processor chip

•Level-two cache memory is optionally installed as a memory module on the system board

Each acts as temporary storage for data and instructions from the main memory. Since the system is likely to use the same data several times, it is faster to get it from the on-chip level-one cache than from the main memory.

The level-two cache memory, when fitted, has a 32-byte line size (a line is an area of memory of a fixed size). It is controlled by the PL/PCI bridge chip (SB82437FX). A single HP cache memory module consists of 256 KB of direct mapped, synchronous or asynchronous, static random access memory (SRAM). The synchronous cache memory module achieves 10% better performance than the asynchronous module.

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