As i mentioned before, it's a first gen sata 6.0 controller that's additionally, not a very good controller in the first place. (being a 9128 marvell).
I run a 256 crucial M4 myself. It's benched read writes are 415-460 read and 260-300 writes, depending on mobo/controller. Considering that I run 292 read and 288 writes, i'm totally hitting my max limit with my sata-2 controller. (keeping in mind there is some small overhead.)
That's not limiting my writes in any way. (for this SSD at least.) My reads, meh, a little. It's so fast you just don't notice.
As I also mentioned before, check your bios to verify that your running your controller in AHCI mode.
As far as the tweaks listed above, there are many tweaks out there, but most do nothing for speed. They mostly serve to keep your SSD lasting along time. Bottom line, tweaks that were meant to help HDD's, hurt SSD's.
Disable your pagefile, disable superfech (in services.msc), disable defragging, and turn off indexing.
Basically all these tweaks do is reduce very unessisary read/writes to your SSD (in otherwords, thrashing) that can hurt an SSD's lifespan due to a finite amount of read/writes they can perform. They do help give you a little more speed on tap, just not noticeable.
There are many more tweaks that can help you, but the ones I listed are the most important. However, staying on track with your current problem, these tweaks will not fix a faulty controller. As I mentioned before, move your SSD to the intel controller, verify AHCI in the bios, reboot. Run your tests, be happier or sadder, then apply the tweaks I posted and reboot.
Be Happy!
My advice costs 1 beer per suggestion!