Clock Throttling - Compaq BL10e - HP ProLiant - 512 MB RAM Introduction Manual

Clock throttling

Clock throttling provides an additional method for lowering processor power consumption.
Depending on the processor model, the system BIOS can either reprogram the processor to run at a
lower frequency or modulate the processor between running periods and stopped periods. Both
methods have the same net effect of lowering the processor's overall power consumption below the
levels available using P-states. The chart in Figure 2 illustrates the relationship between power
consumed and overall performance when P-states and clock throttling settings are used to control
server power. Using P-states clearly provides greater power reduction for a smaller loss in
performance. However, P-states can be used to lower power consumption only to a certain point.
Reducing consumption below that point requires the use of clock throttling.
Figure 2. Power versus performance characteristics for a typical Intel-based ProLiant server with three P-states
400
350
300
250
200
150
100
50
0
0
0 500
DL360 G4 Power vs. Work Done
Clock Throttling slope
0.25 0.5
1000 1500 2000
Relative Performance
Performance
Iterations
P-state slope
0.75
2500 3000 3500
P0
P1
P2
1.0
4000 4500
5