MBP 15 - bootcamp & GPUs

Eason85

macrumors regular
Original poster
Jan 29, 2017
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Hong Kong
To date, is there any way to stop the dedicated GPU from being active while in windows bootcamp? If you disable the card in device manager, will it stop it from drawing so much power?
 

leman

macrumors G4
Oct 14, 2008
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Apple uses a hardware multiplexer to switch between the GPUs. In the PC world, laptops use a software solution. One would need some sort of custom EFI+Windows driver to allow GPU switching (or the use of the iGPU) in Windows. No idea if someone has every attempted anything like that. Doesn't sound trivial.
 

darksithpro

macrumors 6502a
Oct 27, 2016
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To date, is therpe any way to stop the dedicated GPU from being active while in windows bootcamp? If you disable the card in device manager, will it stop it from drawing so much power?

My guess would be that it would be up to AMD/ATI to create a better driver for Windows. Both nVidia and AMD have Optimus and Enduro. The software switches from integrated Intel HD to dedicated Graphics cards based on predetermined software values when running software that benefit from 3D acceleration, such as games and professional productivity programs such as Adobe. So I would suspect that AMD could release a future driver for Windows "if they chose to" that would fully allow you to make the changes you desire if they bothered to in the first place.
 

Eason85

macrumors regular
Original poster
Jan 29, 2017
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Hong Kong
It's strange because normally in Windows you can just disable the device, but it sounds like this is actually a limitation of Apple's UEFI bios setup--they aren't bothered to put the option to switch GPUs in
 

darksithpro

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Oct 27, 2016
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It's strange because normally in Windows you can just disable the device, but it sounds like this is actually a limitation of Apple's UEFI bios setup--they aren't bothered to put the option to switch GPUs in
If the card and the integrated GPU can be changed in OS-X, then there's no reason it cannot be done in Windows. The most logical assumption would be that it is a software limitation when booting into Windows.
 
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leman

macrumors G4
Oct 14, 2008
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My guess would be that it would be up to AMD/ATI to create a better driver for Windows. Both nVidia and AMD have Optimus and Enduro. The software switches from integrated Intel HD to dedicated Graphics cards based on predetermined software values when running software that benefit from 3D acceleration, such as games and professional productivity programs such as Adobe.
As I wrote above, Optimus and PowerXpress/Enduro work very differently from the Apple's GPU switching. Apple uses a hardware solution while the others work in software. That is, Apple actually switches the video output between the GPUs while other solutions do video out through the iGPU while occasionally letting the dGPU render to a memory buffer (that is then displayed by the iGPU).

So its not just about improving a driver, one needs to write a completely new driver for the hardware GPU multiplexer which AFAIK does not exist for Windows.
 
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darksithpro

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Oct 27, 2016
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So its not just about improving a driver, one needs to write a completely new driver for the hardware GPU multiplexer which AFAIK does not exist for Windows.
So basically what you're saying is that if AMD actually spent time on developing a decent Windows 10 driver, the GPU/iGPU switching would actually work, quite well...
 

leman

macrumors G4
Oct 14, 2008
11,006
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So basically what you're saying is that if AMD actually spent time on developing a decent Windows 10 driver, the GPU/iGPU switching would actually work, quite well...
Not really, what I am saying is that someone needs to develop a specialised driver for Windows running on Apple's hardware. I don't really see it as AMD's responsibility to write drivers for hardware they didn't design or sell. This one is on Apple's conscience :)
 
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darksithpro

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Oct 27, 2016
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Not really, what I am saying is that someone needs to develop a specialised driver for Windows running on Apple's hardware. I don't really see it as AMD's responsibility to write drivers for hardware they didn't design or sell. This one is on Apple's conscience :)

That confirms what I just said LOL. It's a software limitation. And because Apple allows their products to boot into Windows that would mean It's ultimately Apples fault. However, because AMD sells a ton of GPU's and a ton of Apple users dual boot into windows, It's pretty lame that they don't include the proper drivers that fully take advantage of the hardware that they sell. Considering the GPU's that are in the current Macbook lineup, It's probably the same chips used in several cheaper windows laptop machines. Sounds like lazy programming to me to be honest.
 

leman

macrumors G4
Oct 14, 2008
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That confirms what I just said LOL. It's a software limitation. And because Apple allows their products to boot into Windows that would mean It's ultimately Apples fault. However, because AMD sells a ton of GPU's and a ton of Apple users dual boot into windows, It's pretty lame that they don't include the proper drivers that fully take advantage of the hardware that they sell. Considering the GPU's that are in the current Macbook lineup, It's probably the same chips used in several cheaper windows laptop machines. Sounds like lazy programming to me to be honest.
Its even worse than that — AMD artificially limits the driver selection (for whatever reasons). The funny thing is that "regular" drivers work perfectly well, the only thing they lack are device IDs.

P.S. I am not aware of any windows laptop shipping with Polaris though, these cards are only for desktops. Which doesn't make any difference to be honest.
 
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Mcmeowmers

macrumors 6502
Jun 1, 2015
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Its even worse than that — AMD artificially limits the driver selection (for whatever reasons). The funny thing is that "regular" drivers work perfectly well, the only thing they lack are device IDs.

P.S. I am not aware of any windows laptop shipping with Polaris though, these cards are only for desktops. Which doesn't make any difference to be honest.
They may lack the device IDs on purpose to due not having been tested at AMD. Now wouldn't the consumer be upset if they enabled the ID and the driver bricked the device.

It takes (practically)no more effort to type an additional ID.

I've never seen AMD market an Apple device for Windows/bootcamp.
 

leman

macrumors G4
Oct 14, 2008
11,006
5,505
They may lack the device IDs on purpose to due not having been tested at AMD. Now wouldn't the consumer be upset if they enabled the ID and the driver bricked the device.
I am sure that you are right. Still, I've been using "modded" (if whitelisting a device ID can even be considered modding) drivers for years, without any ill effect whatsoever.
 
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