Tom's Hardware checked out the compatibility of the AMD Phenom processors and AM2 motherboards and found that in most cases the Phenom plug-in upgrade doesn't work. Eight out of ten motherboards tested in this roundup couldn't handle the Phenom:
I don't really like the conclusion and AMD won't like it either, but the upgrade situation for users interested in replacing their Athlon 64 X2 processor with a quad core Phenom is all but promising. We looked at ten different motherboards to check how well these would work with the new Phenom quad core processor. The vast majority, eight out of ten motherboards, did not work with Phenom at all, which I found a very frustrating result. Yes, Phenom has only been available for roughly one month, and AMD is busy bug-fixing the TLB issue, which certainly came at a difficult moment. However, not being able to run the new processor on existing platforms, as promised by AMD, is both disappointing for those users still interested in using a quad core Phenom processor right away, as well as for AMD, who critically depends on selling its new product.
This result is independent from the chipset used, or from the price category or market segments the motherboards were in. Only Asus and Gigabyte were quick enough to provide a BIOS update, which officially declares Phenom support. However, Gigabyte only provides the update for a mainstream product, but not for the enthusiast model we also looked at. To make things worse, the Gigabyte Phenom update for the mainstream motherboard did not work - at least it doesn't on the 0.2 pre-release sample we had at our disposal for this test.