CTR+ALT+ESC to bring up the Windows taskmanger -> right click on Dolphin.exe -> Click on "Set affinity" -> Untick All Processors -> Select Processor 0 and Processor 1.
If that doesn't improve performance try playing around with selecting Processors, for example processor 0 and 2. You will need to repeat this procedure every time you launch dolphin though.
If that doesn't improve performance try playing around with selecting Processors, for example processor 0 and 2. You will need to repeat this procedure every time you launch dolphin though.