The DRU 810A does write at 48x but Sony set the default read/write speed to 40x to minimize the drive noise.To read and write discs at 48x,u have to activate the Turbo Boost mode.
1) Insert a CD-R/CD-ROM disc into the drive
2) Press and hold the Eject button for five seconds.
The busy indicator blinks twice and the read/write speed switches to 48x. (The Turbo Boost function is active.)
When you open the disc tray, the Turbo Boost function will be deactivated.