Toshiba SSD - Windows 10 - Read speed is fine , Write speed is slow

Hi

I am running Windows 10 64bit on a Toshiba THNSNH256GMCT 256gb SSD.

According to Crystal Disk Mark, I get 500mb/s read, and 250mb/s write

I have installed intel rapid storage technology

I'm not sure why the writes are so slow, at 250mb/s. As benchmarks for this drive show the writes to be closer to 500mb/s:

http://www.technologyx.com/featured/toshiba-msata-ssd-review-256gb/2/
http://ssd.userbenchmark.com/SpeedTest/5507/TOSHIBA-THNSNH256GMCT

I also can't seem to find a way to update the firmware on this drive. My firmware version is 07TA, but I don't know if thats the issue

I'm all out of ideas, so thought I'd ask here

Thanks!