Disabling discrete GPU in Win8 (UEFI) Laptop

Question

Seeing how the Intel HD Graphics 4000 is covering all my needs perfectly for the moment, I would prefer to disable the NVIDIA dedicated GPU in my Lenovo Z400 for a while.

I've already went to the control panel and set the Global Settings for integrated but it still turns on (for a very small amount of time) every now and then.

From my research I would guess I would do it by: (Windows 8):

• Disabling the "NVIDIA GeForce GT 635M" driver in the Device Manager
• Switching from "Switchable Graphics" to "UMA Graphics" in the UEFI settings

I would like to know/confirm if:

• "UMA Graphics" means the Intel HD Graphics 4000 in my case
• The NVIDIA GPU will not actually turn on and generate heat/consume energy, just not be used
• The process is reversible/safe

Specs:

Laptop:    ideapad Z400
OS:        Windows 8.1 (64 bit)
CPU:       Intel i7-3520m (w/ Intel HD 4000)
GPU:       NVIDIA GeForce 635m
RAM:       8GB @ 800 Mhz

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PS: This is a double from the post I made at the lenovo forums.

Answer 1

"UMA Graphics" means the Intel HD Graphics 4000 in my case

Yes, that's what it means. UMA isn't a very common term. In this context it stands for Unified Memory Architecture, referring to how HD Graphics uses system memory instead of dedicated graphics memory. Here is Lenovo Support Specialist specifically confirming what this is.

The NVIDIA GPU will not actually turn on and generate heat/consume energy, just not be used

Yes, that's the purpose of switchable graphics and using HD Graphics. Also confirmed in the previous link.

The process is reversible/safe

Yes, it's reversible by reverting the same settings. I'm not sure what you mean by "safe". If you have an application that requires graphic capabilities beyond HD Graphics 4000, that application will run poorly or not at all.

I would recommend disabling it in the UEFI rather than the Device Manager. This should prevent a utility from re-enabling it. It would also disable it when you are outside of Windows.