Comment by jcranmer

> Why exactly can a CPU contain RAM electronic circuitry, but RAM can't contain CPU electronic circuitry, if both, at the lowest level, the level of the minaturized transistor, the minaturized electronic circuit, are created from the same substrate, the same basic building blocks?

There's different kinds of RAM. CPUs are using SRAM for their caches (which usually have ~6 transistors per bit cell, IIRC, although I'm not a hardware guy, so take this stuff with a grain of salt). Your RAM sticks are using DRAM, which are 1 transistor and one capacitor per bit cell.

Now, this is where my understanding of the actual physical issues really gets sketchy, but the processes that are good at making the CPUs just aren't good at making DRAM, and vice versa. (I would guess that it has specifically to do with the capacitor, but that's purely a guess.) SRAM isn't a problem for the CPU processes, because SRAM cells are closer to the other kind of logic you set up in CPUs.