The chip is codenamed Conesus, packs two cores, 1MB of cache and a DDR2 memory controller. That sits pretty close to the broad specs of Intel's Atom chips, although there's no telling how similar clock speeds, TDPs and, indeed, clock-for-clock performance will compare. Nor does AMD have anything to compete with HyperThreading - although if Conesus is fast enough that won't necessarily be a problem.
As should be expected, Conesus is built on AMD's new 45nm manufacturing process, which will help with power draws. Although comparing Atom to Conesus in terms of TDP won't be particularly fair, as Atom doesn't have an integrated memory controller. As a platform, AMD is predicting sub-25W TDPs from Yukon, which seems pretty good.
There is, however, some indication from the AMD camp that it isn't actually going to be directly competing with Atom anyway.
According to AMD's Computing Solutions Group SVP, Randy Allen. AMD's netbook platform will be addressing "that segment of the mini-notebook that doesn't want that compromised PC experience." AMD's strategy is, basically, to allow Intel to keep the lowest end of the market for itself, and instead capitalise on those netbook customers who want the form factor, but not at the expense of losing a full PC experience.
Allen also clarified that the previously rumoured Bobcat CPU is now codenamed Ontario and will be a netbook CPU with a GPU built into the same silicon die. Don't get your hopes up too soon, though, as it's not scheduled for release until 2011.