AOpen i915Ga-PLF with Power Master

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The board boasts a user friendly BIOS with lots of controls. The SilentBIOS fan control feature we like and wrote about is here, albeit in somewhat modified form, as is a real enthusiast style CPU Frequency/Voltage control page. It is in the latter that the Power Master feature can be controlled.


Power Master feature accessed via Frequency /Voltage Control page in BIOS.

As the screen capture above shows, there are four settings for Power Master:

  • Performance
  • Normal
  • Automatic
  • Silent

The board seemed to default to the Automatic setting; however, the board was first operated in the Normal mode to establish benchmarks. After Windows was fully installed and updated, the Power Master software utility was downloaded from AOpen's web site and installed. This software does not control Power Master; it simply allows you to monitor it. The parameters it monitors and displays on the screen are:

  • S: CPU clock speed
  • L: CPU load in percentage
  • F: Fan RPM
  • V: CPU Voltage
  • T: CPU diode temperature

The stock Intel HSF was installed initially. The temperature in the lab was 22°C throughout the testing.

NORMAL

With Power Master set to Normal, the system behaved... normally. CPU speed was 2.8 GHz as it should be. The SilentBIOS fan control was set to Smart Fan. Here is a quick summary of the observed parameters:

Power Master on NORMAL
CPU Load
CPU Speed
CPU Voltage
AC Power
Fan RPM
idle
2.80 GHz
1.38
76W
2150
max
2.80 GHz
1.35
141W
2600

In Normal mode, the SilentBIOS can be set to any of the three options: Full Speed, Smart Speed or Fixed Speed. (More about SilentBIOS later.)


All three Fan Modes selectable with Power Master in Normal.

AUTOMATIC

With Power Master set to Automatic, the SilentBIOS fan control defaulted to Smart Mode, with 55°C CPU temperature trigger ramp-up speed. The CPU boot speed was 2.94 GHz. This is a 5% overclock from the CPU's 2.8 GHz default speed. It dropped to 1.96 GHz very soon after Windows came up. This is about a 33% underclock from the default CPU speed. Here's a screen shot of the idle screen with the Power Master monitoring utility turned on.


In idle, with Power Master set to Auto.

When two instances of CPUBurn were turned on to apply 100% load to the CPU, the clock speed jumped instantly to 2.94 GHz, the 5% overclock setting observed at boot. The screen shot below shows the on-screen display after about half an hour of CPUBurn. The displayed 45°C temperature was the highest reached with the stock Intel HSF during testing.


After half an hour of CPUBurn with Power Master on Automatic.

These two clock speeds were the only ones observed at the Automatic setting. This was confirmed by running many different applications, singly and in combinations. Unlike CPUBurn, most applications do not keep a constant high load on the CPU. Instead, the load varies dynamically. The clock speed set by Power Master varied just about as dynamically as the load, jumping easily and smoothly between the 33% underclock and 5% overclock. The changes could not be noticed without the monitoring turn on. In other words, it was perfectly seamless throughout the testing.

I found DivX and Windows Media film clips useful in testing. Some screen shots are shown below.


Screen shot from clip of Shark Story. Note the 5% overclock speed and 35% CPU load.


Another film screen shot, this time with clock back down to 1.96 GHz.

In summary, the Automatic setting of Power Master had two direct effects on the system:

  1. In idle or low load, the CPU ran 30% slower than the default speed.
  2. At higher than ~35% load, the CPU ran 5% faster than the default speed.
  3. The clock speed changes were implemented via the front side bus (FSB), which dropped from the 200 MHz default to 140 MHz in idle, and up to 210 MHz at full load.

The clock speed changes had several effects on the system:

  1. At idle, the overall system power consumption dropped to below the norm.
  2. At idle, the CPU temperature also dropped below the the norm.
  3. At maximum load, the CPU performed slightly faster than the norm.
  4. At maximum load, the CPU ran slightly hotter than the norm.

The data is summarized in the table below.

Power Master on AUTOMATIC
CPU Load
CPU Speed
CPU Voltage
AC Power
Fan RPM
idle
1.96 GHz
1.38
68W
1960
max
2.95 GHz
1.35
141W
2600

SILENT

With Power Master set to Silent, the SilentBIOS fan control defaulted to Smart Mode again, with 55°C CPU temperature trigger ramp-up speed. The CPU boot speed was the normal 2.8 GHz. It dropped to 1.96 GHz very soon after Windows came up. This is the same 30% underclock from the default CPU speed as in the Automatic mode.

Power Master on SILENT
CPU Load
CPU Speed
CPU Voltage
AC Power
Fan RPM
idle
1.96 GHz
1.38
68W
1960
max (final)
2.80 GHz
1.35
136W
2600

PERFORMANCE

With Power Master set to Performance, the SilentBIOS fan control could be set to any of the three modes. The CPU boot speed was 2.94 GHz. This is a 5% overclock. It dropped to the default 2.8 GHz very soon after Windows came up. When the CPU was loaded, the clock speed instantly jumped up to 2.95 GHz. These two speeds were the only ones seen in the Performance mode.

Power Master on PERFORMANCE
CPU Load
CPU Speed
CPU Voltage
AC Power
Fan RPM
idle
2.80 GHz
1.38
76W
2150
max
2.95 GHz
1.35
141W
2600

POWER MASTER SUMMARY

There's little to say about Normal mode. There's almost as little to say about Performance mode. It's just a gesture towards overclockers, who would be totally unhappy with just a 5% overclock. Power Master has a significant impact only in the Automatic and Silent modes. The Automatic mode provides the 5% overclock benefit of the Performance mode as well as the 30% power drop in idle. It is probably the most practical mode for most users.

Note: The Vcore drop from 1.38V in idle to 1.35V at 100% load is due to the load on the voltage regulators on the motherboard. It is too small to be significant.

POWER MASTER w/ INTEL 520 CPU SUMMARY
CPU Load
CPU Speed
CPU Voltage
AC Power
Fan RPM
NORMAL
idle
2.80 GHz
1.38
76W
2150
max
2.80 GHz
1.35
136W
2600
PERFORMANCE
idle
2.80 GHz
1.38
76W
2150
max
2.95 GHz
1.35
141W
2600
AUTOMATIC
idle
1.96 GHz
1.38
68W
1960
max
2.95 GHz
1.35
141W
2600
SILENT
idle
1.96 GHz
1.38
68W
1960
max
2.80 GHz
1.35
136W
2600

The Silent mode is a benefit if lowest power consumption is desired. On the other hand, if that is your goal, why would you use a Prescott? Thermals will be improved, on average, especially for office applications where the CPU rarely gets a prolonged workout.

The most important data to compare is between the power draw of the system at full clock speed versus the reduced clock speed implemented by Power Master: 76W and 68W. This 8W difference is not exactly mindboggling. However, we are dealing here with a lowly 520, one of Intel's slowest and coolest 775 P4 models at this time.



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