If I use a discreet GPU with Sandy Bridge, would Sandy Bridge's on-die GPU be sitting idle and be completely wasted?

Question

If I use a discreet GPU with Sandy Bridge, would Sandy Bridge's on-die GPU be sitting idle and be completely wasted?

Or would the on-die GPU somehow work with the discreet GPU and still be productive?

Answer 1

be sitting idle and be completely wasted?

It will not be in use. Just like most IGPs on current gen Core processors.

Answer 2

It depends on what you mean with a 'discrete GPU'.

If you add a dedicated graphics card with its own outputs and only connect you monitors to that then on-die graphics part of the Sandy Bridge will not be used.

If you add a dedicated graphics card with its own outputs and connect monitors to both the outputs of the dedicated graphics card and the motherboards (to CPU/GPU die) part then both will be used. This can be useful when you need more monitors.

If you have a laptop with switchable graphics (e.g. Nvidia optimus) then the onboard chip will always be used. The extra GPU chip can assist with faster calculations, but the actual output is always connected to the on CPU die part and thus it is always used. (Bringing that up since your post mentions a GPU and not a dedicated graphics card.

Lastly, with DX12 both GPU's (dedicated on on CPU die) can be used simultaniously.