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'Optimus technology' is a software [and possibly hardware] solution for automatically switching between an integrated graphics chip or IGP (such as on onboard intel chip) and a more powerful [nvidia] graphics chip. This technology is intended specifically for laptops. The precursor to this technology was 'switchable graphics,' in which the user could manually switch between the graphics card. It may require that the Nvidia GPU has the PCOPY engine.
There is currently no kernel-land support for optimus.
There is currently no kernel-land support for optimus in linux (more below).
== Why is Optimus not currently supported under Linux? ==
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The graphics system in a laptop has a gpu with some memory, in the case of an IGP, this memory may be a piece of system memory, but otherwise it is usually dedicated memory living on the GPU. This GPU connects to a laptop display, or output port.
The first problem is that we do not currently have a way to a priori know what outputs (displays) are connected to what GPU's.
Secondly the supposed optimus software, should perform the task of switching between the which of the two graphics processors drive your display. Ideally this would be done by directly flipping a hardware switch, called a mux ([[http://en.wikipedia.org/wiki/Multiplexer|multiplexer]]). However such a mux does not always exist!
There are two main problems to solve in order to support optimus under linux:
If it does not exist, there there is no physical way to perform this switching of image processing. Thus Optimus is used to effectively "implement" a software mux. Specifically it ensures that relevant data is processed on the right GPU and copied to the device that displays the image.
1) Currently we do not have a way to a priori know what outputs (displays) are connected to what GPU's.
2) The supposed optimus software, should perform the task of switching between the which of the two graphics processors drive your display. Ideally this would be done by directly flipping a hardware switch, called a mux ([[http://en.wikipedia.org/wiki/Multiplexer|multiplexer]]). However such a mux does not always exist!
If a hardware mux does not exist, there there is no physical way to perform this GPU switching. Thus Optimus is used to effectively "implement" a software mux. Specifically it ensures that relevant data is sent to and processed on the right GPU then the data needed for display is copied to the device that displays the image.
When it comes to how a specific machine is configured, there are a number of possibilities:
Again, if the hardware mux exists it would be used to select which GPU drives the internal panel, or the external monitor, or possibly both.
Again, if the hardware mux exists it would be used to select which GPU drives the internal panel, or the external monitor. and possibly both.
It is also possible, that a GPU is hardwired to the internal panel, so the other GPU cannot possibly drive the internal panel. The same goes for external monitor output.
One bad scenario is:the Intel GPU hardwired to the internal panel and the Nvidia GPU hardwired to the external output, with no way to change it.
In the worst case we have that the:the Intel GPU hardwired to the internal panel and the Nvidia GPU hardwired to the external output!
The best case scenario is a mux, which can select which GPU drivers control which outputs.
Basically, you can have ''any'' combination of these possibilities. There is no standard on how to wire things. There should be ways to detect the wirings and whether there is a mux and where, but the documentation is not available to the developers (maybe you can help us figure out how to do this, have any ideas?)
Basically, you can have ''any'' combination of these possibilities. There is no standard on how to wire things. There should be ways to detect the wirings and whether there is a mux and where, but the documentation is not available to the developers (maybe you can help us figure out how to do this, have any ideas? You can also 'petition' nvidia for releasing these specs: [[http://nvidia.custhelp.com/|nvidia customer help]] ? )
Detecting the wiring is not the only hard part. Currently we are missing the entire infrastructure for doing the image copying between graphics cards as described earlier. Everything from the kernel DRM drivers, X drivers and the X server itself need to be modified to support Optimus. Not even the proprietary drivers support it on Linux, save a few exceptions.
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