Seagate tried their darndest to hide the fact that U7 and U9 were 7200RPM, as they never mention the actual spindle speed anywhere in the official documentation, only mentioning "5400RPM class performance" (and 7200RPM + 1MiB U7/U9 may well have performed similarly to 5400RPM + 2MiB drives like Maxtor DiamondMax 16). (Well, I suppose the latency specification gives it away...)

Confusingly, the Desk Reference says the CE version of U9 has 2MiB of cache, which would make it more of a "Barracuda 7200.7 CE". (There was no U7 CE.)

The only "5400RPM" Seagate model released after the U7 was the "Barracuda 5400.1", which was, in reality, the successor to the U Series X, and was actually 5800RPM.