Conroe E6850 on Air, stability test with Ultra_Low_Volt. 
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DailyTech - Intel Core 2 Duo E6850 Spotted in the Wild
The Core 2 Duo E6850 engineering samples are stepping 9 revision E0. Stock voltage on the Core 2 Duo E6850 engineer samples vary between 1.22-1.24-volts.
Core 2 Duo E6850 overclocks very well but dislikes voltages higher than 1.48-volts. When air-cooled, the engineer sample Core 2 Duo E6850 is able to reach front-side-bus speeds of 533-570 MHz, the equivalent of over 2 GHz if you take the quad-pumped bus architecture into consideration.