My AI PC is a $397 open-box HP 24-inch all-in-one: Ryzen AI 5 340, 16GB of DDR5, a 512GB NVMe drive. It runs Gemma 4 12B entirely locally, on the CPU, at about 3 to 6 tokens a second. It works. It is not fast.
I've been pricing the ways to speed it up, and the most interesting one doesn't involve buying a new PC at all. It involves a riser card, an external graphics card, and giving up the machine's only M.2 slot.
The plan: an ADT-Link R43SG — a passive M.2 NVMe to PCIe adapter, about $86 for the Gen4 version — in the M.2 slot, holding a Radeon RX 9060 XT 16GB, with its own power supply. The 512GB boot drive gets evicted from the M.2 slot and moves into a USB-C enclosure, so Windows boots from the rear USB-C port.
Why this could work for local AI, specifically: token generation is memory-bandwidth bound, and once a model is loaded into VRAM, the PCIe link barely matters. Gemma 4 12B in Q4 is about 7.4GB and needs roughly 9.5GB including KV cache at a 32K context — it fits the 9060 XT's 16GB of VRAM with room to spare. The card's 322 GB/s of VRAM bandwidth puts the theoretical ceiling near 46 tokens a second; realistically I'd expect 30 to 45, against the 3 to 6 I get on the CPU today. The external SSD only costs me a slower boot and a ~20-second model load.
The catches, and there are several. The all-in-one has no Thunderbolt or USB4 — its USB-C port is plain 5Gbps — so a proper enclosure like the Sparkle Thunderbolt 5 box I was looking at can't connect at all. This is an open-air riser build, not a tidy dock. The M.2 slot's lane count is unverified, and HP has quietly limited some of its boards to two lanes; the riser needs four, so that's a HWiNFO64 check before I order anything. And Windows doesn't officially support booting from USB — it takes a Rufus Windows To Go build, which Microsoft could break with an update.
The math, for the record: $397 for the machine I already own, $86 for the riser, $650 for the card — about $1,133 before a power supply and the enclosure. The cheapest comparable prebuilt I found, Micro Center's PowerSpec G538 with a 7500X3D and the same card, is $1,399.99. So the riser route is ~$200 cheaper, but the prebuilt gets a real desktop CPU, a full x16 GPU link, a warranty, and a normal Windows install.
I haven't decided. The lane check comes first. If the slot is a full x4, this is the cheapest real upgrade path for the box I already have — and the first time this all-in-one would have a graphics card that deserves the name.