I have a MacBook Pro 13'' (Early 2011) 2.7 Ghz i7, 12 GB ddr3, OSX 10.8.2 (12C60) My HDD died and I decided to replaced it with a brand new SSD SATA III. I bought the ADATA SX900 256 GB and installed it. I made an USB key with Mountain Lion to proceed with the installation. For my surprise, the installation lasted more than 3 hours, when it was supposed to be no longer than 20 minutes. I thought that my internet connection could have something to do with that (but it actually didn't) After 3 clean installs, I have realized there was something wrong with the computer. My computer "works" but it couldn't be any slower. It took it more than 10 mins to start, and it takes it more than 1 minute to respond to any click or action I want it to do. I ran all the tests possible to determine the problem. But as you think, AHT didn't find anything. Also Disk utility said everything was perfect. Then I ran a benchmark test on the new drive, and I saw that it was about 350 mb/s on writing and 500 on reading. The disk was flawless, I double checked I had the EFI last upgrade. I even installed the TRIM Enabler, which worked correctly. I usually don't write in forums, but this is the first time I cannot solve the problem, and there is no info about something like this. I hope anyone here has some previous experience on this matter. Just so you know, I have replaced the disk and used a hdd from another computer and it works like a charm. I also realized that if i put the SSD in a USB SATA case, the computer also works fine. I believe, there has to be a problem with the memory or the processor when the SATA III is active, something that it makes the computer works so hard to access it that it takes forever to actually do something. So the SSD is fine, the computer has no trouble in using from a USB case. But if i use the SATA 3, it saturates the computer (memory??) (Processor) Please help me out here, I don't want to throw away this SSD and get a new HDD.