gpu

After I saw Pineboards 4K Pi 5 external GPU gaming demo at Maker Faire Hanover, I decided it was time to set up my GPU test rig and see how the Pi OS amdgpu Linux kernel patch is going.

I tested it out on a livestream over the weekend, but I thought I'd document the current state of the patch, how to apply it, and what else is left to do to get full external GPU support on the Raspberry Pi.

I also have a full video up with more demonstrations of the GPU in use, you can watch it below:

My journey testing various graphics cards on the Raspberry Pi began soon after the Compute Module 4 was launched in 2020. Since then I've tested almost 20 graphics cards—with a little success.

But there were two roadblocks to getting drivers for even older AMD radeon drivers working well:

I'm working on a project—a very dumb project, mind you—and I was trying to acquire the two current-gen flagship GPUs: an Nvidia RTX 4090, and an AMD Radeon RX 7900 XTX.

In some weird stroke of luck (it has been difficult to find either in stock), I was able to get one of each this week.

(lol at the size difference...)

Besides exorbitant price gouging, Nvidia's ownership of the crown in terms of GPU performance remains in this generation, as the 4090 blows past any competing card so far. But AMD's 7900 XTX was poised to be the best value in terms of price, performance, and efficiency (at least compared to any Nvidia offering).

In October 2020, after Raspberry Pi introduced the Compute Module 4, I started out on a journey to get an external graphics card working on the Pi.

At the time, it'd been over a decade since the last time I'd built a PC, and I had a lot to learn about PCI Express, the state of graphics card drivers in Linux, and PCI Express support on various ARM SoCs.

Last year, due to some extreme luck and help from a viewer, I picked up an AMD RX 6700 XT for MSRP (around $500).

My initial goal was to see if I could get the card working on a Raspberry Pi. Though my initial effort was fruitless, I've since hacked the driver to work through at least a few 'rings' of AMD's doorbell init process.

Earlier today I did a livestream on my YouTube channel to attempt using an Nvidia GeForce GTX 1080 on a Raspberry Pi Compute Module 4.

As with all my testing, I'm documenting everything I learn in this GitHub issue, which is part of the Raspberry Pi PCI Express Card Database website.

It's only been a few hours, but I've already gotten good suggestions for better debugging than I was able to do on the stream. And someone pointed out it might be the case, due to 32-bit memory limitations on the BCM2711's PCIe bus, that no GPU with more than 4 GB of onboard RAM could work. Though it's hard to confirm there'd be no software workaround—even 1 and 2 GB graphics cards (AMD and Nvidia) are crashing the kernel in similar ways.

The full livestream is available on replay and is embedded below:

Last year I tested two older graphics cards—a Radeon 5450 and a GeForce GT710—on a Raspberry Pi Compute Module 4.

This year, I've been testing three more graphics cards—a GeForce GTX 750 Ti, a Radeon RX 550, and the diminutive ASRock Rack M2_VGA.

The Compute Module 4, if you didn't know already, exposes the BCM2711's single PCI express lane, and the official IO Board has a nice, standard, 1x PCIe slot into which you can plug any PCI express device.

The Raspberry Pi Compute Module 4 eschews a built-in USB 3.0 controller and exposes a 1x PCI Express lane.

The slightly older Raspberry Pi 4 model B could be hacked to get access to the PCIe lane (sacrificing the VL805 USB 3.0 controller chip in the process), but it was a bit of a delicate operation and only a few daring souls tried it.

Watch this video for more detail about my experience using these GPUs on the CM4:
GPUs on a Raspberry Pi Compute Module 4!

I've been a Mac user for years, and I've repaired hundreds of different Macs, from the early II series to the latest 2015 and 2016 model MacBook Pros, iMacs (and other Apple hardware to boot!), and there is almost never a hardware situation where I've thrown in the towel and told someone to ditch their Mac.

The 2011 MacBook Pro has, for almost a decade, been the exception to that rule. There was a major flaw in the AMD Radeon GPUs included with that model year's logic board which seemed to cause GPU failure either due to overheating, internal chip problems, BGA solder joints getting broken, or a combination of the above. The problem was so rampant, Apple was forced to set up a free repair program for affected MacBook Pros—though the 2011 model has since been dropped from that program. I've handled three 2011 MacBook Pros (none of them my own—I had an Air back then), and all three of them were scrapped because of the GPU issue.