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Display your CPU's true speed
Authored by: tmlundvall on Dec 08, '03 01:30:26AM

I would be willing to bet, that all of you are seeing the effects of Apple's new "Processor and Bus Slewing" technology at work. The basics of this technology, is that when the computer senses that it is only being used at a small portion of its capabilities, it slows the bus AND processor speeds down to conserve power, and reduce heat. When the computer detects a higher demand of the processor, it kicks back up to the faster speed. Since a lot of what we do with a computer would be the same speed running at 500 Mhz as 1 Ghz, who cares? Typing email, browsing the internet, typing command line commands, will likely put the computer into the slower speed, and when you check the system speed, it will show the slower speed. The reason you can't see the difference in most cases, and the benchmarks don't show any difference, is that the computer is able to make these adjustments efficiently enough, so that it is undetectable to the user. The following is excerpted from Apple's Developer page.

http://developer.apple.com/documentation/Hardware/Developer_Notes/Macintosh_CPUs-G4/12inchPowerBookG4/1_Introduction/chapter_2_section_6.html

Processor and Bus Slewing


To lower power consumption and heat generation, the 12-inch PowerBook G4 incorporates an automatic power management technique called bus slewing. Bus slewing is designed to run at high processor speed, bus speeds, and voltage when the demand on the processor is high, and to run at low processor speed, bus speeds, and voltage when the demand on the processor is low. Switching between different processor/bus speeds and voltages is achieved by a transition that operates seamlessly to the user and should not impact system or application performance.


The 12-inch PowerBook G4 allows the user to control bus slewing mode. The options for specifying either high, reduced, or automatic processor and bus speeds are located at System Preferences>Energy Saver>Show Details>Options>Processor Performance; then select Automatic, Highest, or Reduced.


Slewing is enabled with the automatic setting. The default processor performance setting for the 12-inch PowerBook G4 is automatic.


If the 12-inch PowerBook G4 detects a system temperature that is too high, due to high ambient temperatures or other factors, it will automatically force the system to reduced speed mode regardless of the selected setting.


When the 12-inch PowerBook G4 is in slewing mode, the processor, processor bus, and memory bus dynamically adjust their speeds based on the current needs of the system. The processor speed will switch between 1000 MHz and 766 MHz and the processor bus and memory bus will switch between 133 MHz and 102 MHz.



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Display your CPU's true speed
Authored by: zipping on Jan 04, '04 07:52:15AM

I don't buy what Apple is trying to tell us here...."Don't pay attention to the clock speed returned in the terminal..." What are they hiding from us. Why is my 800 MHz PowerBook G4 really returning 677 MHz. Maybe they just want to avoid a class action? I want this problem resolved Now! Proof, not chatter !

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Believe only a half of what you see or are told by others, and you will be half right most of the time!



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Display your CPU's true speed
Authored by: nvannote on Jan 15, '04 04:39:08PM

See my response to your previous post in this thread...



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