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HP Vectra VL 5/xxx Series 5 User Manual

Page 31

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31

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,
2.5 or 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.

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.

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.

Processor

Frequency

M1

PL Bus

Frequency

M2

PCI Bus

Frequency

M3

ISA Bus

Frequency

PL Frequency

Multiplier M1

M3

VRM

1

SW-1

SW-2

SW-8

SW-3

SW-4

SW-7

75 MHz

2

1.5

50 MHz

2

25 MHz

3

8.33 MHz

Closed

Closed

Closed

Open

Open

Open

Vcc

90 MHz

2

1.5

60 MHz

2

30 MHz

4

7.5 MHz

Closed

Open

Closed

Open

Open

Closed

Vcc

100 MHz

2

1.5

66 MHz

2

33 MHz

4

8.25 MHz

Open

Closed

Closed

Open

Open

Closed

Vcc

120 MHz

2

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 MHz

2

3.5

66 MHz

2

33 MHz

4

8.25 MHz

Open

Closed

Open

Open

Open

Closed

Vmmx