I recently updated my BenQ DW1620 to the DW1655 and noticed that when burning +R DL discs (Verbatim), the highest ripping speed is 2.4x even with Overburn enabled in QSuite 2.01. On the DW1620, I was able to burn the same discs at 4x with no problems. I checked +R and +RW discs with the DW1655 and they will burn up to the specified speed and higher with no problems.
As far as I know, the retail version of the DW1655 shipped with the latest firmware so I have no clue why +R DL discs won’t burn at the suggested 8x speed for Verbatim discs. If anyone has some insight on this situation, please don’t hesitate to respond b/c I would love to burn these discs at 8x!!