Actually, matrix-matrix multiplication is where analog computing really shines. A multiplication operation can be done with a single transistor: one operand is

Actually, matrix-matrix multiplication is where analog computing really shines. A multiplication operation can be done with a single transistor: one operand is gate voltage, another one is source to drain voltage. The resulting current through the transistor is proportional to the product of the two. An addition operation is even simpler: it's just connecting two wires carrying two different currents - the resulting current on the output wire will be the sum (due to Kirchhoff laws). Of course, you pay for this efficiency with precision, which for some applications (e.g. neural networks) can be a reasonable trade off.