How can I automatically switch between integrated graphics and dedicated graphics on Bootcamp?

Question

I have been running Windows 10 on Bootcamp for awhile, but the thermals and the fans have both been irritating while streaming video or web browsing.

With MacOS, there is the option to automatically switch between integrated and dedicated graphics to help combat both of those things, is there any way I can do that with Windows 10 on Bootcamp?

I'm using a MacBook Pro 15" with a Radeon Pro Vega 20.

Answer 1

Yes

Unlike most other laptops, MacBook Pros with dGPUs use a graphics muxer to physically switch which GPU is pushing pixels to the display. By contrast, most other laptops simply share a framebuffer which both GPUs push to and the display can read from via some methodology. If you want to read about this more, I recommend you read up on the Linux kernel's documentation or Arch page on hybrid graphics. The long and short of it though is that the unique hardware architecture of the MacBook Pro means that it can't just operate like most other laptops.

Under macOS (and Linux), this is handled by the OS and drivers sending the appropriate commands to the hardware and switching when needed. However, although Windows does have graphics switching, it isn't as well integrated with Macs. To solve this, by default, MBPs with dGPUs boot into Bootcamp with the iGPU disabled—something that, as you've discovered, can be problematic.

For reasons, this is a particularly sticky issue with eGPUs. As such, the eGPU community has developed tools to get around this by making your MBP think it's booting into macOS, thus keeping the iGPU enabled. I strongly recommend you read the entirity of the Boot Camp eGPU Setup Guide thread (even if you're not going to use an eGPU), but the basics steps are as follows:

1. Use automate-eGPU EFI to set up the custom bootloader (or rEFInd it if you want to use an external drive.)
   1. Download automate-eGPU EFI to a USB drive or internal partition formatted as FAT
   2. Boot to the drive by holding down Option during boot
   3. Install Intel graphics drivers
2. For users of 2016 and 2017 15" tMBPs (not you!), use 0xbb’s integrated.bat to set the GPU you want attached to the display.
3. Install AMD drivers.

At this point, you should be able to switch between your GPUs!

If you're feeling brave, I'd also recommend you use AMD drivers from BootCampDrivers rather than the stock AMD ones. Unfortunately, the stock AMD drivers are very poorly optimized for Macs; these drivers are modified to better support Macs. Note that since they're modified binaries, there's no source to view, and you're trusting that the author to write good code. That said, I personally trust them, and the benefits are real.

Answer 2

Boot Camp eGPU setup on a Mac can be plug-and-play for some and a total nightmare for others. The easiest Thunderbolt 3 Mac to pair with an eGPU is one that has Intel integrated graphics only such as the 13″ MacBook Pro and 2018 Mac mini. Mac computers with a discrete graphics card often require more resources and Windows isn’t always very compliant. Error 12 (lack of resources) or flickering/stuck Windows logo at boot are primary issues when connecting an eGPU in Boot Camp. Now that Apple officially supports external graphics cards in macOS (since 10.13.4), we’ve devoted more effort to set up and maintain a functional external GPU in Windows 10 via Boot Camp. In the past three years, our community has provided many different solutions [External Graphics Card build guides]. This Boot Camp eGPU setup guide is a collection of those efforts.