strange hard drive specification

[Smalltalk80]

I'm thinking of choosing a 80G (5400rpm) hard disk instead of the default 60G for my T60 purchase, but I don't know the cache sizes, so I look at Lenovo's accessory store for detailed specification, but the result I get is really weird:

Comparison results

All Thinkpad SATA drives say their maximum transfer rate is 150Mbps (how can 7200rpm be the same as 5400rpm?), except that the 80GB one has an astonishing 493Mbps!
(I'm not sure whether it's Bps (as shown in comparison page) or bps (as shown in individual pages)

For cache size, all drives have 8MB (including the 60G one), but the 80GB one has only 2MB (even if it's $20 more expensive than the 60G one)

Can any one explain this? Just some typos?

[killigrew]

Hi, its not the maximum Speed of the Harddrive but the Speed of the SATA Interface.
Thats why the 5400 and 7200 have the same transfer rate.

Dont now why the last one have such an High transfer rate,
even if it has an SATA2 Interface it would only be 300MBps.
perhaps its a typo.

cu