Work out memory bandwidth instantly with clear inputs, formula shown and shareable results.
Peak bandwidth is transfers per second times bus width in bytes times channels. Real bandwidth is 70-90% of that because of refresh, bank conflicts, read/write turnaround and command overhead — the efficiency term is where memory controller quality shows.
Memory bandwidth
BW = data rate x (width / 8) x channels; effective = peak x bus efficiency
Refresh, activate and precharge commands, read-to-write bus turnaround and row conflicts all consume bus cycles that carry no data.
More channels, higher data rate, or wider buses. HBM takes the wide-and-slow route with 1024-bit stacks, saving power per bit.