New CPU
I replaced my CPU with a week 28 part, and it runs at significantly lower voltage and slightly higher speeds than my old week 24 part. This configuration is silent: all fans <=600 RPM.
User name: cmthomson
Stability: 13+ hours Orthos
E6600
OC: 3333 MHz (9x370)
Stepping: 6 B2...
Actually for a week 24 chip it's not uncommon.
The fastest this chip will go at 1.45v is a bit above 345 FSB (3110 MHz).
At 1.40v it's solid 300 FSB; I didn't experiment much with that voltage.
The week 27 chips need less voltage.
UPDATE:
With better ducts installed, I was able to boost the voltages and clocks and still keep the system silent, with all fans < 700 RPM.
User name: cmthomson
Stability: 20+ hours Orthos
E6600
OC: 3289 MHz
Stepping: 6 B2
Week: L624
Code: A819
Vcore: 1.55 (BIOS)
Cooling: air...