Six GPUs on One X16 Slot: R9700s and RTX 3090s Behind a PCIe Switch
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Ranked by a public rubric, not by votes: what a comment adds counts, not who wrote it. How comments are ranked · Comment rules
Summary
Doug Calobrisi describes running six GPUs from one x16 slot on a consumer X570 board: four Radeon AI PRO R9700s and two RTX 3090s behind a Broadcom PEX88096 switch, each card on its own x8 link. On the R9700s, Qwen3.8-27B at TP4 reports about 4,700 tokens/s prefill at 32k and 601 tokens/s across sixteen clients. The numbers are the author's own, unsourced measurements on one setup. The build also needed custom kernel modules for BAR sizing.