Warning: CMP801: Global Output GLB of PLL instance <PLL name> is floating and the core output <core output name> is being used. This will waste one global resource.

There are a finite number of global resources. YB and YC are core outputs from the PLL but they still use up the global resources if they are used alone.

Action

Actel recommends that you use the Global outputs (GLA, GLB, GLC) in conjunction with the core outputs; do not leave the Global outputs floating (this is a waste of resources). If you use GLB plus YB then you use only one global (same for GLC and YC).