I recently had a look at the manual for the Gigabyte Z87MX-D3H motherboard, and there is a clear BIOS option to "disable" the onboard VGA (I'm guessing this is in reference to the Intel iGPU on Haswell CPUs).
I will be using discrete graphics so this is ideal. I would prefer to shut down that bit of silicon to save power, reduce heat etc. There is also one less piece of hardware to cause software conflicts.
However, I am also looking at the manual for the Gryphon Z87 (had to RMA the Gigabyte and getting an Asus Gryphon Z87 as a replacement). There doesn't seem to be any option to disable the onboard VGA. There is an option to use the PCIE graphics adapter as the primary output for display, but nothing about actually turning off the CPU's iGPU.
Does anyone know how I can go about doing this on the Asus board? Not be able to do so would be a major disappointment.
Or have I simply misunderstood the option on the Gigabyte board, and this setting simply causes the output from the PCIE card to be the primary, without actually shutting down the iGPU?