Concerning the Buffer Under Run
I noticed these buffer under runs specificaly hardware ones. I mean the software buffer from the burn proggy was *FULL but the burner's one was keeping full -> empty -> full -> empty on a 2-3 seconds basis.
I'm used to run a little handy software called Vcool (but loads of others do the same) which keep my Athlon Thunderbird no too hot (like 23Â°C just now) when it does idle.
This little prog can also set some VIA chipset option usually located in the bios.
My conclusion is: If forced cooling is on (for Vcool it means both NBCoolBit checked AND Idle Loop checked) then I get everytime buffer under run. The solution was to check Master Read Caching in PCI Option of Option menu.
I no longer have to choose between Buffer Under Runs and cool Cpu
The attached image speaks for itself. When speed is ok (4X all time) I did switched off cooling OR if cooling was enabled, then Master Read Cahcing was on.
For me this problem is definately solved. Period.