Default [Q] Emulators laggy when plugged into HDMI out

Hey there, As the title states, just wanting to do some emulator game playing on my TV and figured my Nexus 10 would work great.

I got the bluetooth controllers up and running pretty easily, and the games run great on the tablet itself, but when I pop in the HDMI cable the FPS immediately drops (especially on N64 games) and the games become borderline unplayable. Unplug the HDMI cable mid game and everything is back to normal. I assume this has something to do with scaling to two different resolutions, but I'm not sure if there is some fix/workaround (either turning off the tablet display or scaling the tablet display maybe?). Any recommendations would be great!