Many cdroms have another set of jumpers apart from the csel,master and slave. On an Aopen 52x I just installed the pair nearest the ide cable was jumpered. When I put it in the bios said it was mode4. When I tried the other positions one would not work, but the other got the bios to recognize it as DMA2. I can't find anything about these jumpers from AOpen. I have seen them on other cdroms. Anyone have an explanation?