HP XA manual Bus Frequencies, Switch, Local Bus

2 System Board

Devices on the Processor-Local Bus

Bus Frequencies		There is a 14.318 MHz crystal oscillator on the system board. This frequency
		is multiplied to 66 MHz by a phase locked loop. This is further scaled by an
		internal clock multiplier within the processor.
		For example, the Pentium II 300 MHz processor multiplies the 66 MHz
		system clock by 4.5. Switches 1 and 2, on the system board switches, set the
		frequency of the Processor-Local bus, which for all HP Kayak XA PC
		Workstation models, is 66 MHz. Switches 3, 4 and 5 set the clock multiplier
		ratio.
		Switch		Processor				Switch2		Frequency
	Processor				PCI Bus	ISA Bus				Ratio
				Local Bus
	Frequency				Frequency	Frequency				Processor:
		1	2	Frequency1			3	4	5
										Local Bus
	233 MHz	Open	Open	66 MHz	33 MHz	8.25 MHz	Open	Closed	Closed	3.5 : 1
	266 MHz	Open	Open	66 MHz	33 MHz	8.25 MHz	Closed	Open	Open	4 : 1
	300 MHz	Open	Open	66 MHz	33 MHz	8.25 MHz	Closed	Open	Closed	4.5 : 1
	333 MHz	Open	Open	66 MHz	33 MHz	8.25 MHz	Closed	Closed	Open	5 : 1
	1.Processor bus frequency is always set at 66MHz for all XA PC Workstations models.
	2.Switches are provided to match the system board to processor frequency when a

system board repair is performed.

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.

Setting the switches to operate at a slower speed, than the processor is capable of supporting, can still cause erratic behavior in some cases, and would reduce the instruction throughput in others.

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