What are the extra jumpers for?

[techs]

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?

[MacGyver]

Digital audio out?

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[AlienDyne]

Leave it as it is. The second set of jumbers is for factory use only.

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