NEC-ND3550A Reading and Writing Problem

I have purchased a NEC-ND3550 DVD Writer, and installed in my new dell system successfully. But, it is reading and writing at 1.2-1.3x only. The system has anothe 16X-DVDROM drive that came along with the system. This is reading upto 6X speed. The ND3550 came with firmware level 1.05, and I flashed with 1.06 from NEC download site. Did any one come across this situation? I really appreciate if you have any suggestion to overcome this problem … Thanks

Try to connect the NEC-ND3550 as primary instead of slave. Also make sure that the UDMA is 4 for this IDE.