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I have the hp ProBook 450 G3. The EFI is enabled and the Arch is working fine. But if I go to the BIOS setup and select an option with an "intuitive" name "Disable legacy and disable secure boot" (maybe not quite verbatim), then the secondary monitor (plugged via HDMI) says me: "There is no signal". When I select an option "Enable legacy..." in the BIOS all works as usually.
Maybe I do need to append some logs etc -- I may do this.
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Those appear to be limitations of your hardware. Do you have the computer manufacturer's latest firmware (BIOS) installed? If all works well, why change it until it does not?
Regards
UNIX was not designed to stop you from doing stupid things, because that would also stop you from doing clever things. -- Doug Gwyn
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It seems that this behavior was not depending on that option in the BIOS actually, because I have played with the BIOS parameters without a luck. A second screen has got working after I has reinstalled the EFI partition.
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