For heat dissipation you want the most surface area per volume (because you can only transfer heat away in the surface area). The optimal arrangement for that would be a huge, flat, one atom thick surface.
Another goal we have is low latency (and high clock rate, which is depenend on low latency), which suggests putting everything in a qube or even a shere. So we compromise somewhere in the middle with a square with a few layers.
Another goal we have is low latency (and high clock rate, which is depenend on low latency), which suggests putting everything in a qube or even a shere. So we compromise somewhere in the middle with a square with a few layers.