MHz and Mbps (or Hz and bps, for that matter) are completely different units of measure so that they are unrelated. And it's not "bytes per cycle," it's "bits per cycle," or "bits per second" for bps.
I was thinking frequency (400 MHz) when I should be thinking throughput or speed (400Mbps), and they're unrelated to each other, so technically speaking, he was correct and I was wrong.
