Highest effective transfer rate on SATA II
Solution 1:
I have a SATA II motherboard and a SATA III Crucial M4 SSD that can read above 400MB/s. With the AS SSD benchmark tool I get 265MB/sec read rate, indicating my maximum SATA 2 throughput.
I should point out that the main benefit of a SSD is not maximum transfer rate, but low latency and fast random access. You still get all those benefits on SATA 2, so it's well worth it.
To cover a real-world file transfer scenario unrestricted by drive performance, I copied a 8GB file from a SSD to another SSD with TeraCopy. It yielded an average speed of 141MB/s, indicating a total of around 280MB/s throughput.
Solution 2:
A little bellow 300MB/s. You can read more here: http://www.tomshardware.com/reviews/sata-6gbps-performance-sata-3gbps,3110.html Also: http://en.wikipedia.org/wiki/Serial_ATA
"Second generation SATA interfaces run with a native transfer rate of 3.0 Gbit/s, and taking 8b/10b encoding into account, the maximum uncoded transfer rate is 2.4 Gbit/s (300 MB/s)."
If you put that SSD on SATA II you should expect +/- 300MB/s.