i didn't know you could install the pvr card on the core, if so how can you send the order to start recording from an MD, also, does timeshifting work in this scenario?
It's a feature of MythTV. The MD is setup as a slave backend, the Core is the master backend. Either can house the pvr card. The features are the same whether the pvr card is in the MD or in the Core. The benefit is your MD doesn't have to be one for recordings.