is something unclear…we will can use zambezi cpu on our AM3 platform?or we need a new socket?
John Fruehe September 7, 2010
Zambezi will work in AM3+ only.
emphasis mine. Bulldozer is backwards compatable with the latest Opteron sockets, but not AM2+/AM3. It'll need new motherboards.
In the main blog article is this:
Bulldozer will fit into the current “Maranello” and “San Marino/Adelaide” platforms. “Maranello” is our high performance platform that will support up to 4 CPUs. Combining a “Maranello” platform with the upcoming 16-core “Interlagos” processors, the total core density of a 4P system will reach as many as 64 cores.
Unfortunately, it's also been confirmed by AMD to work in AM3.
There was a change somewhere in the plans on whether it was going to work or not and different people are saying different things. Kyle of Hardocp specifically asked them at Hotchips and got a yes. (CBA to link).