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Re: Possibility for switching Hardware MUX


Hi Michael,

On Sunday 07 October 2012 11:58:23 Michael wrote:
> in BIOS I have an option to select Graphics between switchable and 
> discrete. When switching to discrete, the intel VGA controller 
> disappears completely from lspci. This makes me thinking that there must 
> be an additional hardware multiplexer in my machine??? Am I right, that 
> those hardware MUXes are usually switched using ACPI? It would really be 
> nice to find out, which ACPI command switches the MUX in either 
> direction. Switching off the nvidia card already works even though i am 
> using the proprietary driver, as the nouveau driver seems not to support 
> my card good enough.
The Lenovo enterprise laptops (like the Thinkpad W520) have the same options 
for choosing between discrete/integrated/optimus (and maybe even switchable 
graphics, but I am not sure on that). These machines have a hardware 
multiplexer I guess, otherwise it is not possible to provide those options.

ACPI is a subsystem that also communicates with the BIOS, but I doubt that you 
can switch graphics on-the-fly.

> Attached you can find my DSDT, which might be interesting for your 
> projects as well.
Please provide the raw acpidump output, there might be more relevant tables 
like SSDT. Do it for the different BIOS settings, I have seen an Acer laptop 
that shows different ACPI tables depending on whether the 
discrete/integrated/optimus mode is in use.


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