Today I present a fine piece of engineering, carefully assembled inside a custom chipboard chassis: the 2400cc Inference Racer, a.k.a. my winter heater. Power comes from two second-hand AORUS RTX 3090 XTREME WATERFORCE cards. One glows a beautiful teal, the other red. I have no idea why, nor how to change it, so apparently this is now the official color scheme. The whole thing is managed by an independently powered Lenovo ThinkPad motherboard with a Ryzen 7 7840U and 64 GB RAM. No battery, screen, keyboard, case, or other unnecessary luxuries attached. The naked motherboard is cooled by a custom aluminium water block, way too much Arctic cooling paste, and a sophisticated mounting mechanism known in the industry as a clamp. Cooling is provided by a €24 VW Golf radiator, connected through a carefully curated collection of vaguely compatible hoses, fittings, adapters, and optimism. The loop holds around 2.4 litres of coolant, hence the 2400cc displacement. Current reliability is excellent: it leaks less than 100 ml/day, especially as long as it doesn't get too warm. PCIe topology is equally sensible. One GPU is connected through the ThinkPad's WWAN slot at PCIe Gen4 x1, while the second uses an SSD slot at Gen2 x4. The BIOS had to be patched to remove the hardware whitelist, modify the PCIe power-up sequence, and disable PCIe power-saving states. The SSD slot is technically capable of Gen4 x4, but "technically capable" and "stable" turned out to be different concepts. The two 3090s are connected through NVLink, which fortunately means the questionable host PCIe arrangement matters much less once inference is running. It currently runs Ubuntu and serves Qwen3.8-27B through vLLM, quietly and at surprisingly decent speeds. I'm still tuning the setup for performance. And it can also boot completely without the 3090s. In that configuration it becomes a low-idle-power server and can run smaller models on the 7840U using its 64 GB of shared system RAM, Vulkan, and llama.cpp, ideal for our resident Hermes bot named Hoot. Still not managed to enable hot swap though. Peak home inference engineering.   submitted by   /u/TooManyPascals [link]   [comments]