None of the processors with separate caches tested in this review can perform fast data transfers between the cores. Intel’s Core Duo (Yonah) and Conroe, each with a shared L2 cache, are the only processors that ensure fast processing of the same data block by two cores, yet their speed is limited too when the common data are modified.
Ultimately, this is an architectural limitation, a legacy of Intel and AMD dual core being based on their dual CPU designs. This doesn't mean that future CPUs won't be enhanced by letting them directly read each other's caches – In fact, it makes sense that Intel and AMD may move in exactly that direction. Now, whether or not other companies CPUs do this, such as IBM, is another story.