I recently dropped an OWC Mercury Extreme 1.0 GHZ into my sawtooth G4. Everything seems to be stable and solid for the most part, but it seems when the machine is under heavy CPU load it sounds like a fan is speeding up or someting. When the CPU load is removed the it drops back instantly. Anybody know if the fan on the OWC upgrade is a temperature controlled fan? If it is it must be only 2 speeds. It's as if I get a higher pitched fan noise coming from the machine under full CPU load... Anybody experience this?