And maybe some specific SATA controller. Your numbers look good for most SATA controllers.
I just bought this "Mushkin Enhanced MKNP22SC240GB 240GB PCIe 2.0 x2 MLC Internal Solid State Drive (SSD)" from here:
I installed it in my Dell XPS 8700 tower (here's the screenshot):
And then installed Windows 8 pro on it.
I then ran the Parkdale SSD speed test and got these results:
So as you see, it showed:
Read: 290 MByte/s
Write: 238 MByte/s
When the specs on the NewEgg page said "Up to 825MBps" reads.
So now I'm thinking why are my numbers so low. I installed it into only available slot I had, which is PCI-ex4. Does that have something to do with what I'm seeing?