Devices On The Processor-Local Bus; The Intel Pentium Microprocessor - HP Vectra VE5 3 Series Technical Reference Manual

Bus Frequencies

Devices on the Processor-Local Bus

The Intel Pentium Microprocessor

The Pentium processor is packaged in a pin-grid-array (PGA), which is
seated on the system board in a zero-insertion-force (ZIF) socket 7. Only
upgrades that are pin compatible with the original processor, manufactured
by Intel, are supported.
P54C chips, working at 75, 90, 100 and 120 MHz (new versions), and P54CS
chips, working at 133 and 150 MHz, require a simple 3.3 V supply, and so are
powered directly from the regulated 3.3 V output of the power supply.
P54C chips, working at 120 (old versions), 166 and 200 MHz require slightly
more than 3.3 V; and P55 chips require slightly less (2.8 V). They each need
an active VRE voltage regulator module (VRM), in which the voltage is
derived from the 3.3 V, 5 V and 0 V outlets of the power supply. Since there
is no VRM in the HP Vectra VE 5/xxx series 3, these types of processor
cannot be installed.
Any thermal contact material between the processor and the heat-sink must
not be removed or disturbed. The cooling needs of the processor are critical.
There is a 14.318 MHz crystal oscillator on the system board. This frequency
is multiplied to 50, 60 or 66 MHz by a phase locked loop. This is further scaled
by an internal clock multiplier within the processor. For example, the
Pentium 100 MHz processor requires the 66 MHz system clock to be
multiplied by 1.5. Jumper J7, on the system board, sets the frequency of the
Processor-Local bus; switches 1 and 2 on the switch bank, SW2, set the clock
multiplier ratio.
J7 Setting for 50 MHz
2 4
1 3
The table on the following page summarizes all of the recommended
combinations of jumper and switch settings, along with a few non-
recommended combinations (shaded in grey) for completeness. Note that
only the 100 MHz, 120 MHz and 133 MHz settings are used on models at the
time of the first release.
J7 Setting for 60 MHz
2 4
1 3
2 System Board
Devices on the Processor-Local Bus
J7 Setting for 66 MHz
2 4
1 3
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