Before I thought it was only possible if you had an AMD 710southbridge or higher if memory recalls.
But now it looks like it is possible on a AM3 board with an Nvidia SLI chipset?
http://www.asus.com/product.aspx?P_ID=1g8o5Sh3csqM5M8u&templete=2
Core Unlocker
Intelligently Unlocks True Core Performance
ASUS Core Unlocker simplifies the activation of a latent AMD CPU—with just a simple swtich or hot key. Enjoy an instant performance boost by simply unlocking the extra cores, without performing complicated BIOS changes.
But now it looks like it is possible on a AM3 board with an Nvidia SLI chipset?
http://www.asus.com/product.aspx?P_ID=1g8o5Sh3csqM5M8u&templete=2
Core Unlocker
Intelligently Unlocks True Core Performance
ASUS Core Unlocker simplifies the activation of a latent AMD CPU—with just a simple swtich or hot key. Enjoy an instant performance boost by simply unlocking the extra cores, without performing complicated BIOS changes.