trans am when u r testing with crystal disk use 1000MB file because u r testing the cache speed of the controller... thats why u r not taking stady results. try to test big files like 500MB 1000MB and 2000MB to avoid the cache from the controller. U said that u have test it in 4x and 8x the speed of 4x is 2000MB/s in Ver.2 pcie and for x8 is 4000MB/s speeds that even i cant get... so u dont have any problems with that. now the cache speed yes may be diff. but this is at least of ur problems. Every benchmark that u r using needs a diff. setup to ur controller like in IOmeter u have to dissable everything to get maximum results in it. Just search the forum for each setup with benchmarks. Computard me and stevero have post some setups. take a look of them and make one new post to see what is ur problem each time. We r here to help u understanding this controller how it perfom each time