A hacker recently managed to successfully get the PCIe slot on a Raspberry Pi Compute Module 4 to support a PCIe GPU. The hacker, who goes by the handle Toble_Miner (@Toble_Miner) on Twitter, posted the fruit of his labour online, after what looks like a fair amount of tinkering.
Based on their postings, Toble_Miner managed to get the Module 4 tinker board to work with what appears to be a Delock mini-PCIe card, based on SIlicon Motion’s SM750. Of course, due to its nature, the functions of the card is limited to providing 2D graphics and video-playing capabilities for embedded applications, plus the odd servers and thin clients. Specs-wise, the card only has four cores running at 300MHz, plus 100MB that is borrowed from the 256MiB DDR3 RAM that’s on the Module 4.
And when I say surprisingly well I mean it:
With just 2x 1GHz MIPS 1004Kc cores (HT, MIPS32R2, LSB) and 256MiB of RAM on a single DDR3 channel it hardly breaks a sweat while delivering passable web browsing experience pic.twitter.com/zodnVAk4j3
— Toble_Miner | tsys (@Toble_Miner) February 19, 2022
For the record, Raspberry Pi tinker boards that carry these slotless PCIe connectivity ports aren’t uncommon. However, the number of enthusiasts within the board’s community that actually choose to exploit the port are far and few, to the point that you could count them by hand. Figuratively speaking, of course. For Toble_Miner, their endeavour also required some messing around with the latest Raspberry Pi OS Bullseye OS, primarily due to the Broadcom PCIe host “hating write combining”. It’s at this point that Toble_Miner attracted the attention of Jeff Geerling, who then directed them towards his GitHub page, where he keeps a list of PCIe devices compatible with the Compute Module 4.
You can follow Toble_Miner’s journey towards getting his GPU efforts to work via his Twitter page, as well as visit Geerling’s GitHub repository for a better understanding. It’s an interesting and somewhat fun journey to read up on, especially if you’re a budding tinkerer.