Comment by adrian_b
8 hours ago
In modern computers, the throughput of an execution unit is the same for multiplications and additions, but multiplication frequently has a greater latency, by 1 or 2 clock cycles.
Many CPUs, like the AMD Zen CPUs, have more execution units that can do additions, than those that can do multiplications. So the aggregated throughput over all execution units can be higher for additions than for multiplications.
For example, for floating-point numbers, the AMD Zen CPUs have 4 vector execution units, where all 4 can do additions, but only 2 of them can do multiplications or fused multiply-add operations. So Zen CPUs can do up to 4 additions + 2 multiplications per clock cycle (when 2 multiplication-addition pairs are fused).
> Many CPUs, like the AMD Zen CPUs, have more execution units that can do additions, than those that can do multiplications
And the reasons for that it takes way more transistors to implement a fast rabbit^W multiplier than to implement a fast adder, so adding an execution unit that cannot multiply is easier to warrant than adding one that can.