I have found no difference. ST31000333AS SD15 flashed to SD1B OS: WinXp SP3 CPU: Intel Q6600, overclocking turned off for benching HD Tach 3.0.4.0 used I had no issue with my drive - it was only used as a backup disk. Decided to flash it to the new firmware. After flashing, WinXP detected a hardware change, and a new hard disk. During the flashing process, the HDD made a few clicking noises (not unlike the click of death I used to hear from my IBM Deskstar aka Deathstar drives years ago), but it finished ok, and the BIOS detected the new firmware as SD1B. SD15 BIOS Random access 15.3ms CPU utilization 4% Average read: 99.3 MB/s SB1B BIOS Random access 15.2ms CPU utilization 4% Average read: 98.8 MB/s There were a few clicks at the start of the test, which I thought the system had hung, but the bench finished ok. That point is seen in the graph (red line). However, lots of clicking sounds from the drive at random times since I've updated the firmware. I'm not sure if that's a good sign. The system almost seems to pause when that happens.