The last thing to investigate is the "PCI Master Read Caching". This is a quick one :
 
Activity 1003 PCI M.R.C. disabled 1003 PCI M.R.C. enabled  
idle >40°C 28°C (as in the first table)  
 
So this Option is a "must enable" for everyone.
 
In the 1003 BIOS Setup set the following : Advanced - CHIP Configuration - PCI Master Read Caching : Enabled
 
Avez vous testé cela ?