> Why don't they start making CPUs 3 Dimensional like a cube with 6 "processors" each with multiple cores as its "sides" with the pins on the opposite sides of

> Why don't they start making CPUs 3 Dimensional like a cube with 6 "processors" each with multiple cores as its "sides" with the pins on the opposite sides of the cube wall. Not directly an answer to this specific question, but a (somewhat) colleague who writes his PhD thesis about 3-dimensional chip design made a popular scientific lecture about this topic. As I understood it, the central problem is that it is very hard to produce chips with multiple (lots of) layers (where you want to have interconnects inbetween). In particular producing the interconnects between the layers is really hard if they can lie "everywhere" instead of only at the border. There exist multiple ideas how this might be done (e.g. drill holes with high-precission lasers into the substrate and try to fill them with something conductive), but none of them as of today "really works" (at least if we are talking about chips with somewhat more than 4 layers and interconnects everywhere inbetween).