2 System Board

Devices on the Processor-Local Bus

Bus Frequencies

The location of the system board switches is shown in the diagram on page

 

20. Five of these switches (SW-1,2,3,4 and 7) determine the working

 

frequencies of the PC, and the three frequency multipliers (M1, M2 and M3),

 

as summarized in the table below. The uses of the other switches are

 

summarized on page 39.

There is a 14.318 MHz crystal oscillator on the system board whose frequency is multiplied, by a phase locked loop, to 50, 60 or 66 MHz for the Processor Local (PL) bus, according to the settings of SW-1 and SW-2. This is further multiplied, to the processor core frequency, by a factor of 1.5, 2,

2.5or 3, according to the settings of SW-3 and SW-4. The PCI bus works at half the frequency of the PL bus. The ISA bus works at a third or a quarter of the frequency of the PCI bus, according to the setting of SW-7.

You will need to change these switches when you replace the original system board, for a repair, so as to match the processor. You will not need to change the switches if you upgrade the original processor using the correct Intel Overdrive. It is not recommended to upgrade to another processor that may have different voltage requirements.

Processor

M1

PL Bus

M2

PCI Bus

M3

ISA Bus

PL Frequency

Multiplier M1

M3

VRM1

 

 

 

 

 

 

Frequency

Frequency

Frequency

Frequency

SW-1

SW-2

SW-8

SW-3

SW-4

SW-7

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

75 MHz2

1.5

50 MHz

2

25 MHz

3

8.33 MHz

Closed

Closed

Closed

Open

Open

Open

Vcc

90 MHz2

1.5

60 MHz

2

30 MHz

4

7.5 MHz

Closed

Open

Closed

Open

Open

Closed

Vcc

100 MHz2

1.5

66 MHz

2

33 MHz

4

8.25 MHz

Open

Closed

Closed

Open

Open

Closed

Vcc

120 MHz2

2

60 MHz

2

30 MHz

4

7.5 MHz

Closed

Open

Closed

Closed

Open

Closed

Vcc,Vre

133 MHz

2

66 MHz

2

33 MHz

4

8.25 MHz

Open

Closed

Closed

Closed

Open

Closed

Vcc

 

 

 

 

 

 

 

 

 

 

 

 

 

 

150 MHz

2.5

60 MHz

2

30 MHz

4

7.5 MHz

Closed

Open

Closed

Closed

Closed

Closed

Vcc,Vmmx

 

 

 

 

 

 

 

 

 

 

 

 

 

 

166 MHz

2.5

66 MHz

2

33 MHz

4

8.25 MHz

Open

Closed

Closed

Closed

Closed

Closed

Vre,Vmmx

 

 

 

 

 

 

 

 

 

 

 

 

 

 

200 MHz

3

66 MHz

2

33 MHz

4

8.25 MHz

Open

Closed

Closed

Open

Closed

Closed

Vre,Vmmx

 

 

 

 

 

 

 

 

 

 

 

 

 

 

233 MHz2

3.5

66 MHz

2

33 MHz

4

8.25 MHz

Open

Closed

Open

Open

Open

Closed

Vmmx

1.Where there is a choice indicated, install the one that is appropriate for the given processor.

2.These processors are not available for these models of HP Vectra PC at the time of printing. This information is provided for completeness only.

The computer may execute erratically, if at all, or may overheat, 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.

31