AnandTech got their hands on a dual-core Penryn and compared the chip against the current Conroe platform.
Penryn is the overall family name but there are two cores in particular that we'll be talking about today: Wolfdale and Yorkfield.
Wolfdale is a dual-core desktop Penryn core with a 6MB L2 cache shared between the two cores. Yorkfield is two Wolfdales on the same package, giving the quad-core CPU a total of 12MB of L2 cache.
Wolfdale and Yorkfield are architecturally identical, so performance per core is no different between the processors - Yorkfield simply has more cores.
In the performance tests they've found that the dual-core Wolfdale is about 5% faster clock-for-clock than Conroe, while consuming approx. 10% less power under load and 3% less at idle. Check it out over here.