End August 2014 I bought my Samsung SSD 840 EVO 1 TB and put into operation. After just six weeks Useful life is the reading speed of approximately 525 MB / sec to 80 MB / sec and thus decreased more slowly than normal hard drives. Files are read more slowly with age. Freshly written data are not affected. Hence many benchmarks provide seemingly correct results since its test write these files only fresh on the tested SSD. In some forums for computer technology is discussed and informed on the subject. Some users have already noticed that your computer has been slow, studied the problem but first woanderns and not in the SSD.
The problem has now been confirmed by Samsung and is working on a solution. This is a bug in the firmware of the SSD. This affects not only the SSDs with 1 TB volume but smaller models of 840 EVO series. Mid-October to appear a new firmware and the user must then probably play or let this play. Before a complete backup of all data would be advisable ........
I hope that there will soon be a problem solution. Nevertheless, the Bug is a severe shortage, so this review only two stars.