These reading speeds are for Pressed (Commercially released) DVD media. DW1620 can read DVD Recordable (DVD+/-R) media at a max speed of 8X.
@gwiz, my wild guess is that your 1620 did not read the diskÂ´s Media type (MID) correctly, it though that it is reading a pressed DVD and it did that at 16X max speed.
..just my opinion... any ideas anybody?
EDIT: sorry goes to SAPA, got a cup of fresh coffee and did not see your post on time...