Basically for whatever reason enabling multicore rendering in the video settings doesn't work, so you'll have to paste this into your autoexec file:
cl_threaded_bone_setup 1
cl_threaded_client_leaf_system 2
r_threaded_client_shadow_manager 1
r_threaded_particles 1
r_threaded_renderables 1
r_queued_ropes 1
studio_queue_mode 1
cl_threaded_bone_setup 1
mat_queue_mode 2
gmod_mcore_test 1
