I have a laptop with the Intel HD3000 and a discrete Nvidia GPU. It is mentioned that the HDMI is linked to the HD3000.

So, when I connect my laptop to an external display via HDMI-out, the HD3000 will be the active card. If I then start gaming, can both cards be active at-once?

The whitepaper here seems to state the two are multiplexed. Does this imply only one can be used at a time?


When rendering to your laptop's integrated screen, both video cards will (or at least can) be active at the same time. Optimus begins to run into problems when multiple outputs are involved, though. My personal experience has been that only the integrated screen's framebuffer is shared by the two GPUs, and external connectors such as HDMI or DisplayPort are connected exclusively to one card or the other. For example, monitors hooked up to the external connectors of my Dell XPS L502 are rendered exclusively by the Nvidia gpu - the Intel HD Graphics adapter is not even aware of those monitors.

If your research indicated that the HDMI port for your laptop was connected to the Intel HD 3000 card, most likely anything rendered to that screen would be rendered exclusively by the Intel card. The difficulties described in this similar question would appear to support this conclusion.

As mentioned in that thread, the NVidia Optimus Test Viewer is a very useful tool in determining which applications are being rendered by which hardware. I suggest experimenting with this tool and both the integrated screen and an external connector to determine definitively which graphics cards can be used on which screens.

  • I need to clarify, if this is a laptop I am thinking of buying, can you look at the specs and state if the HDMI would be rendered exclusively by the Intel IGP? – Anirudh Ramanathan Dec 7 '12 at 16:41
  • I'm afraid the specs / description on that page are a little vague - "Optimus" is not even mentioned, though I do see both an Nvidia and an Intel VGA driver in the downloads section. Some cursory googling indicates that optimus is indeed present but I can't find any information specifically on the external ports. I would suggest contacting Asus directly and asking them this question. Which GPU is connected to which ports is something that can vary between implementations with Optimus-enabled machines. – Fopedush Dec 7 '12 at 17:15
  • I'm thinking it isn't possible. In the question here, the user is sporting the same combination. Will contact ASUS and check. – Anirudh Ramanathan Dec 7 '12 at 17:20

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