[Solved] Sata iii ssd needs a sata iii motherboard?

First, The SATA 3 6Gb/s ssd performance will be reduced to SATA 2 3Gb/s levels. That is very well documented.

Second, forget about synthetic benchmarks. Actual solid state drive performance will be less than published specifications and benchmarks for a variety of technical reasons. That too is well document. On top of that different benchmarks produce different results that do not reflect real world performance.

Third, the calculations are incorrect. It is Gigabits per second not Gigabytes per second. World of difference. You also need to factor in the 8b/10b encoding overhead. The theoretical maximum data transmission rate for SATA 2 3Gb/s is 300MB/s. The theoretical maximum data transmission rate for SATA 3 6Gb/s is 600MB/s. The theoretical maximum is commonly referred to as the burst rate. It is almost never achieved and anything close to it can only be maintained for a very very brief moment.

Fourth, the real world performance difference between SATA 2 and SATA 3 ssd's is almost negligible. Typical users normally can't tell the difference between SATA 2 and SATA 3. A user would have to use a benchmark to measure the difference.