Your Mac does have a SATA 2 interface, therefore the max speed is ~270 Mb/s.
But this is NOT what is important.
Courtesy "VirtualRain" :
"The problem with assessing storage speed is that vendors always publish sustained transfer rates (STR) or in other words, max sequential read/write speed. A typical laptop HD has a max STR of about 100MB/s. A modern SSD can do about 500MB/s. And you'd think, wow, that's 5x faster. And you're right, but that's not even close to the reason SSD's seem so fast.
The fact is, as I stated in my long essay a few posts back, is that most desktop usage is random small block I/O. On this kind of storage profile, access time becomes king... not STR. Now a typical laptop HD has an access time of around 5-8ms with extreme values of perhaps 100ms or more if the head happens to be on the wrong part of the disk. On the other hand, SSD's have access times around 0.04 or 0.05ms. Thats 100X better performance than an old-fashioned HD.
So the reason SSD's are game changers, is not the fact that they have 5x the sustained sequential transfer rate of an old HD. It's the fact that they have 100x less latency for random I/O. (Although as I said above, that 5x STR improvement coupled with RAID0 can become a game change for managing large media files)."
