Sony Dru 800a burning DVD-RW too slow


I have SONY DRU 800A which works fine when I work with CDRs and CDRWs but when i burn DVD-RW the 3.5Gb data takes 3.5 hours to burn. I updated firmware from sony site still no change. Drive instolled on secondary cable as a master, primary has HD 40Gb as a master and 160GB as a slave. IDE all set up to DMA. OS - windows XP SP2. Software NERO OEM Nero disc drive tool shows x8 speed.

Need your bright heads help, what do i do wrong and what twicks I should make.