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To be able to use a secondary screen you need to be running on your discrete graphics card. It all comes down to some Mac hardware specifics quirks.

When booting in legacy boot mode on mac hardware with two cards the discrete card is not available for use and powered of completely.

  1. You need to boot in EFI mode for the discrete card to be visible. (To quickly test this part ust try booting on a usb stick in EFI mode and you should see two cards with lspci)

  2. Then Switch to using the discrete card using vgaswitcheroo as root run:

echo "DIS" > /sys/kernel/debug/vgaswitcheroo/switch Blockquote

to switch to the discrete card. This should be run from console with X session stopped.

To be able to use a secondary screen you need to be running on your discrete graphics card. It all comes down to some Mac hardware specifics quirks.

When booting in legacy boot mode on mac hardware with two cards the discrete card is not available for use and powered of completely.

  1. You need to boot in EFI mode for the discrete card to be visible. (To quickly test this part ust try booting on a usb USB stick in EFI mode and you should see two cards with lspci)

  2. Then Switch to using the discrete card using vgaswitcheroo as root run:

echo "DIS" > /sys/kernel/debug/vgaswitcheroo/switch Blockquote

to switch to the discrete card. This should be run from console with X session stopped.

To be able to use a secondary screen you need to be running on your discrete graphics card. It all comes down to some Mac hardware specifics quirks.

When booting in legacy boot mode on mac hardware with two cards the discrete card is not available for use and powered of completely.

  1. You need to boot in EFI mode for the discrete card to be visible. (To quickly test this part try booting on a USB stick in EFI mode and you should see two cards with lspci)

  2. Then Switch to using the discrete card using vgaswitcheroo as root run:

echo "DIS" > /sys/kernel/debug/vgaswitcheroo/switch Blockquote/sys/kernel/debug/vgaswitcheroo/switch

to switch to the discrete card. This should be run from console with X session stopped.