Owners of Samsung’s 840 EVO SSDs report speed issues with their drives. The users found that files that were recently written to the disk were read at full speed (450 MB/s), however files that were written to the disk longer ago, were read with a 100MB/s or less.
The problem was demonstrated with HD Tach, benchmark software that is able to read out the entire disk. The benchmark clearly shows that the sequential read speed of older data varies a lot, while the read speed of recently written files continuously stays at the same level.
Samsung has stated it is aware of the problem and that it works on a firmware update to fix the problems. The company expect the update will be read mid October.