How do I specify what video card to use for display in windows?

Posted on

QUESTION :

I have two Nvidia GTX 580s and a GT 610. I use the 580s to do architectural renderings and I want to use my 610 for display, so my 580s arnt wasting processing power managing the display. Because of my motherboard layout, and because the 580s take up 2 slots, I have to have the 580s on PCIe slot 1 & 2 with the 610 on 4 (3 is covered by the second 580). There is no other physical configuration for the cards.
I called my motherboard manufacturer, and there is no setting in the BIOS to set which PCI slot is my default display, nor is there a BIOS upgrade to do this.

So, my question is this:
Is there a way to set this in Windows? Even if the screen is blank until windows loads and switches to my 610 for display, that’s fine.

Thank you in advance for anyone who can help me 🙂

ANSWER :

If the cards are not in SLI, then they are treated as separate PCI-E devices.

Windows’ behavior for video adapters plugged into PCIE (on a system without Nvidia Optimus or anything else to complicate matters) is the following:

  1. Every video adapter gets its GPU booted, which means that the kernel loads firmware into the GPU and initializes it. This, with the Nvidia device drivers, turns on the compute (OpenCL/DirectCompute/CUDA), OpenGL and Direct3D functionality of the card, and also initializes proper power management for each card. Note that cards in SLI are treated as one logical video adapter in Windows’ opinion, but each card still gets booted.

  2. The video adapters are enumerated, starting from the first one detected (which should be the one in the first PCI-E slot), looking for an electrically connected display. The video adapters know which displays are connected and what resolutions are available because they have smart port detection, which means that when you plug in the monitor, the GPU knows.

  3. Windows uses the list of video adapters and corresponding monitors to determine where to allocate the primary window station (primary desktop). This “window station” is assigned to the lowest-numbered PCI-E adapter with one or more displays connected. If it has 0 displays, it is skipped.

If the 580s don’t have any display connectors plugged into the back of them, then they still have their VGA controller initialized, but it’s not actively being used for graphics rendering at all… it’s just sitting there waiting for something to be plugged in. Meanwhile, a certain amount of the graphics infrastructure has to be loaded in order to allow for computing architectures (OpenCL, DirectCompute, etc).

Leave a Reply

Your email address will not be published.