Six GPUs on One x16 Slot: R9700s and RTX 3090s Behind a PCIe Switch

An engineer successfully configured six graphics cards—four AMD Radeon AI PRO R9700s and two NVIDIA RTX 3090s—on a single x16 slot of a consumer motherboard using a Broadcom PCIe switch. The setup runs Debian 13 with ROCm and CUDA side by side, utilizing a custom initramfs module to handle large memory base address registers and kernel options for peer-to-peer traffic and tensor math acceleration. Open article →