I have a HP 754N (P4 2.53 about 2.5 years old) and am trying to burn at 16X on a BenQ1620. I get great burns and quality scans at 12x, but as soon as the recording speed goes over 12.4x the device buffer drops to below 30% and fluctuates between 30%-85% until the end of the disc. The burner also slows to about 10x when this happens until the end of the disc. It takes over 7 min to burn at 16x. I just made sure that it is on a 80 wire cable and DMA2 mode.
Any other ideas to check out would be greatly appreciated.