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Originally Posted by Aptmunich
No I don't, but I would say that OS X uses the graphics capabilities to power quartz extreme that display effects such as Exposť, the genie effect, resizing etc...

So if you could slow the GPU, you might notice slowdown in general system graphics performance...

Ok all, so update on the underclocking of the iBook's Radeon 9200. I found a program called "ATIccelator II" which adds a systems preferences pane that allows you to raise or lower your ATI graphics card's GPU and memory clock speeds.

I discovered the default settings are 183mhz for the GPU and 190mhz for the VRAM. I downclocked both of these to 100mhz (roughly a 45% drop-off in clock speed for both). First of all, I noticed zero stability problems through a/b 12 hours of uptime. Secondly, I noticed no lag in the general system performance. My guess is that while some older powerbooks and iBooks, with less powerful GPU's and less VRAM might have rendering speed issues at a lower clock rate, the newer ones are more than powerful enough to run smoothly even while downclocked. Thirdly, I noticed a/b a 12 minute increase in battery life, from a/b 4:03 hrs to right at 4:15 hrs. A small increase, but an increase nonetheless.

If anyone else wishes to try this please post your results here.

iBook G4 1ghz (1.07ghz in system info)
768mb RAM
30gb HD
Airport Extreme
OS X 10.3.6

Amd AthlonXP 2600+ @ 2.2ghz (10x220mhz)
Epox 8RDA+ rev. 2 mobo
512mb PC2700 @ 220fsb
GeforceFX 5950 Ultra
60gb HD / Floppy / DVD-RW+/-
WinXP Pro
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