The Kentsfield based Core 2 Quadro QX6700 (quad-core, 2.66 GHz) can outperform the Core 2 Duo X6800 (dual-core, 2.93 GHz) by as much as 80% in favourable testing circumstances. This is pretty impressive.

Generally speaking, the shortcomming of parallelism is that the more independant factors involved, the less efficient the whole is. These tests suggest that Quad Core can in fact be just as efficient as Dual Core, although admittedly, these tests were pre-approved by Intel.

AnandTech reports.