The water-cooled one using an i7-975 overclocked to 4.5 GHz is on an EVGA X58 mobo. That's my 737NG cockpit FSX PC. The i7-920 air-cooled one running at 4.0 GHz in on a Gigabyte EX58-UD5. That's running my Aerosoft (Oz) Piper Arrow cockpit with FSX.
Regards
Pete