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Never heard of this before. Maybe it's old hat for you PC tweakers out there. Anyway, the G5 Powermac controls procesor speed to manage heat -- as much as 700MHz variance in the dual 2GHz Powermac! It is said to be handled without imparting a performance hit to the end-user, but it's surprising, nevertheless. The user can set a preference for the bus, but the system will override it when it needs to:

http://www.xlr8yourmac.com/index.html#S16104
 

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Wow, never heard of that about the Power Mac G5's. Interesting.
 

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Its actively used in laptops where heat and power are the major issues. Though, many people weren't expecting to see such practices in a desktop machine. A very interesting topic, and now we know how Apple helped make the G5 so quiet (the fans only go as fast as they have to).
 

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http://www.macrumors.com/pages/2003/09/20030907030313.shtml
<blockquote>
Speed ranges involved start from 1.3GHz up to the highest rated GHz of the chip (1.6, 1.8, or 2.0). The default slewing option for the PowerMac G5s is Automatic, and the processor and bus speeds are modulated seamlessly to the user.

According to our contacts, there should be no performance loss in Automatic mode.

That being said, at least one user (in the previously mentioned thread) claims an 11 point increase in their Xbench score after changing their Slewing mode from Automatic to Highest. However, readers are reminded that XBench has been inconsistent in producing reproducible benchmark numbers -- even on the same machine. MacRumors' reader 1stunna managed to get a 11 point increase in Xbench scores by simply rerunning the test three times, with no other changes to the system</blockquote>

Apple's Developer Document on it has more info.

Also, This Ars Technica Thread
<blockquote>
Normally, the machines are running at about 2/3 their total clock speed (for 2GHz machines, this is 1.4GHz), this jumps up to the full speed whenever it's required. The ramp time up or down is ~1ms, but the CPU is running normally during this time, so there is no performance "hiccup". This results in about 60% power/heat savings, which jumps up to about 85% savings if the machine is idle and they "turn on other power saving features". When idle, the CPU fans are barely turning.
</blockquote>

Eeeenteresting.

--PB
 

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Transmeta processors do that. Actually............... I think IBM makes Transmeta processors!!! :eek: I going look into that ;)

Ah Ha!! I found it Transmeta and IBM

[ September 09, 2003, 07:10 PM: Message edited by: Jordan ]
 
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