AMD SATA performance is horrid. You can rollback the driver in device manager or switch to MSAHCI. I have the faster 1TB version and even my numbers are well below what it is known to be able to do, only hitting near my old Vertex 460.
Update: New benchmark, same low performance, just so you can see it isn't because of the age of the benchmarks. Have since enabled RAPID mode, hence the jump in sequential performance.
i couldn't rollback the driver because i did some updates but i return it back to the system driver i think it, is a little better, And the as ssd benchmark is reading that i have storachi-ok so how can i change it to MSAHCI as you suggested . thanks