Intel's 2013 Haswell architecture may includea L4 cache that can be shared between the CPU and the GPU. The primary reason for the new cache layer would be to significantly improve graphics performance.
While as-yet unannounced by Intel itself, the claim comes from VR-Zone which claims to have spotted evidence that the Haswell launch line-up will include desktop chips featuring integrated graphics some two or three times faster than the best Ivy Bridge has to offer.
The biggest change, however, comes in the form of a new layer of cache memory. In addition to the usual L1, L2 and L3 cache layers, VR-Zone claims Haswell is to ship with a chunk of L4 cache. Traditionally, such a feature is limited to expensive chips aimed at the high-performance computing (HPC) market.