Switchable graphics different between M17xR4 and M18xR2

Does anyone know why Dell implemented the switchable graphics differently between the M17xR4 and M18xR2?

The M17xR4 can switch between 7970M/HD4000 and 7970M only.

The M18xR2 can switch between 7970M and HD4000.

I prefer the M18xR2 implementation because I can force my system to run only on the HD4000 for better battery life. There doesn't seem to be a way to do this on the M17xR4.

 

The reason for this is that the integrated chip was designed to support optimus technology. Therefore, when you switch graphics in the M17x R4, the card will be disabled but it'll still show up in the device manager. You'll notice this right away if you run a benchmark as the AMD card will be inactive.

 

The design of the M18x is superior in many ways, but that particular difference makes the M18x a better platform not only for battery life, but driver support is also easier. Hybrid switchable graphics is more difficult to support than the on/off mux switch in the flagship.

 

Taking this chance, let me ask this: do/does 680M/SLI support optimus? AFAIR 580M didn't. Is optimus available in M18xR2?

 

Thankfully, no. Neither the M18x R1 nor the R2 has hybrid switchable graphics such as Optimus or Enduro. The beauty of the M18x is you choose to run discrete graphics or integrated graphics. FN+F7 prompts a reboot to switch. All power to the PCIe slots is turned off when the IGFX is active, and the IGFX is disabled when discrete graphics is selected. It's awesome, and there's no proprietary technology to muddy the waters or cause technical issues. Battery life and performance are enhanced depending on your selection, and headaches are minimized. There are no whitelists to fuss with and no drama coaxing drivers to install.



Based on the technical details we received from Louis Bruno (Alienware's Lead Mobile Graphics Engineer - hope I have the title correct) in one of our conference calls, CrossFire and SLI are incompatible with hybrid graphics switching, so it would not be something that could be properly implemented even if someone had a reason to want that.

 

Thanks for the explanation. I prefer M18s implementation much better. The M17xR3 is also implemented like this. I'm surprised they changed this for the R4.

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Personally, I prefer the M17x R4 implementation. It's better to have a choice between Optimus/Enduro enabled switchable graphics and discrete graphics. If my DGPU were ever to fail, I could always revert to using just the IGPU, without exorbitant expenses. It just takes a little extra effort and initial configuration.