Multiple GPUs in a Skull Canyon NUC

Every 3 years at Canonical we get a laptop refresh fund. I used my last one to buy a ThinkPad T450. My next one is due in November this year. I was considering replacing the ThinkPad with a desktop computer of some kind. I can certainly keep the T450 for portable work, but I mostly sit at the same desk all day, so figure I may as well get a desktop rather than a laptop.

I recently mentioned to my friend and colleague - Martin Wimpress, that my ThinkPad T450 was becoming a bit long in the tooth. There's a Linux Kernel bug somewhere which causes the GPU to lock up randomly when driving 3 displays (internal + two external monitors) which is annoying when you are trying to work on it. It's also struggling to cope when doing a bit of heavy video work - such as having multi-party video meetings, while other things are happening.

On hearing this Martin told me he had a "spare" desktop I could use, as it's sat gathering dust at his place. Once he explained the specs and what I'd be borrowing, I jumped at it. So now I'm typing this blog post on an Intel Skull Canyon NUC. It's a bit nice! I've never used a computer with an illuminated skull on the lid before :D

The interesting thing about this computer is it features a combined Intel CPU/GPU and AMD GPU on one board. The Intel i7-8809G sports a 4-core 8-thread 3.1GHz main CPU and HD Graphics 630 on-board GPU. However, it's bundled with a discrete AMD Radeon RX Vega GPU too. 

What's even more neat is the NUC has a ThunderBolt port which means I can attach an external GPU should I wish. I wish, so I have. The only GPU I had kicking around was an nVidia GeForce GTX 960 (a hand-me-down from another PC which was recently upgraded to an nVidia 1050Ti).

So now this computer technically has 3 GPUs, Intel, AMD and nVidia.

alan@robot:~$ sudo lshw -C display
description: VGA compatible controller
product: Polaris 22 XT [Radeon RX Vega M GH]
vendor: Advanced Micro Devices, Inc. [AMD/ATI]

physical id: 0
bus info: pci@0000:01:00.0
logical name: /dev/fb0
version: c0
width: 64 bits
clock: 33MHz
capabilities: pm pciexpress msi vga_controller bus_master cap_list rom fb
configuration: depth=32 driver=amdgpu latency=0 mode=1920x1080 visual=truecolor xres=1920 yres=1080
resources: iomemory:200-1ff iomemory:210-20f irq:191 memory:2000000000-20ffffffff memory:2100000000-21001fffff ioport:e000(size=256) memory:db500000-db53ffff memory:c0000-dffff
description: Display controller
product: HD Graphics 630
vendor: Intel Corporation
physical id: 2
bus info: pci@0000:00:02.0
version: 04
width: 64 bits
clock: 33MHz
capabilities: pciexpress msi pm bus_master cap_list
configuration: driver=i915 latency=0
resources: iomemory:2f0-2ef iomemory:2f0-2ef irq:188 memory:2ffe000000-2ffeffffff memory:2fa0000000-2fafffffff ioport:f000(size=64)
description: VGA compatible controller
product: GM206 [GeForce GTX 960]
vendor: NVIDIA Corporation
physical id: 0
bus info: pci@0000:40:00.0
version: a1
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress vga_controller bus_master cap_list rom
configuration: driver=nvidia latency=0
resources: iomemory:2f0-2ef iomemory:2f0-2ef irq:17 memory:c4000000-c4ffffff memory:2fd0000000-2fdfffffff memory:2fe0000000-2fe1ffffff ioport:3000(size=128) memory:c5000000-c507ffff

Cats and dogs living together!

Bit weird, not gonna lie.

I haven't fully exercised these capabilities yet. I did one quick test to see if I could use OBS to live stream a window being displayed with the AMD GPU, but with the stream encoding done via nvenc on the nVidia GPU. That seems to work well. What a time to be alive! 

Thanks Martin, you're not getting this back. :D

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