The CompServ AGA ScanDoubler II description reads like it has physical jumpers for some settings.
Jumpers the other cards do not need because they detect and change automatically?
I dont own one, but it sounds like you have to physically change jumpers if you want to use 15KHz, 48KHz or 64KHz modes.
If true, it sounds like a major PITA to me - switching jumpers when you want to use special modes.
It could just be that these are debug registers to switch off certain features if there is a problem.
Maybe under normal operation you have them all ON and you can use any mode just like the others?
If they were just for debug, why are they in the manual?
If anyone has the English manual or reads German and can translate better than Babelfish, then maybe we could tell?