The transfer-rate ceiling is 64 / 8 × 3.2e9 = 25.6 GB/s per channel before protocol, controller and workload effects. Effective bandwidth cannot be inferred from width and transfer rate alone. State the request pattern, channel mapping, locality, competing and coherency traffic, refresh policy, measurement boundary and accepted useful bytes over elapsed time. Multiple channels increase aggregate capacity only when mapping and concurrency let the workload use them.

Common trap: width × freq only.

It is the workload- and configuration-specific region where additional offered load causes queues and a chosen latency percentile to rise sharply. Find it by sweeping a stated replay and measuring accepted traffic, queue occupancy and latency percentiles. Set the operating target below the measured failure point with headroom justified by bursts and corner variation; do not assume one percentage of peak applies to every system.

Common trap: Confusing with clock frequency knee.

A stall percentage alone cannot prove this. First compare required bandwidth with the width-and-clock ceiling. Count accepted useful bytes, then correlate gaps with request occupancy, target supply and consumer readiness. If a controlled experiment shows a downstream bytes/s limit unchanged by widening, that limit bounds the gain. Multiple limits can coexist: a path may need both greater admission capacity and a wider data channel to meet its target.

Common trap: Proposing wider bus without stall data.