ATI HD5570 driver in CentOS-5-i386 - Linux

Hardware
CPU:Xeon 5506/1366(4 Cores)
MB:ECS X58B-A
RAM-DDR3 1333 4G*3
VGA:ARI HD 5570
OS:CentOS5 i386

Problem:
My PC become very slow, slower than Core 2 Quad PC(RAM 8G)
I doubt that the ATI driver installation in incomplete.
CPU has been used in the average of 60%! Even a simple
operation of computer, such as opening a webpage, system
still very slow.

I tried to remove the ATI dirver, because my youtube
screen will become blank after driver installation.

Before I install 5570's dirver, the default driver in
CentOS5 causes 20% CPU comsuption.

But everything goes wrong,even I re-install CentOS.
How can this be?

So, after looking discussions in PTT, I know that:
ATI driver sucks!

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