Buying Used GPUs for Local LLMs

As of 2026-10-07 (run counts, sourced only); prices are the 2026-09-28 snapshot from our weekly snapshot. Used prices move weekly — treat every figure as a snapshot.

TL;DR

What our board actually runs on used cards

Used cards are a real, active segment of our data — not a footnote. The CMP 170HX alone has 16 sourced runs, more than many new consumer cards.

RTX 3090 used — the default

The 3090 is the most-submitted used card class in the community for a reason: 24GB, CUDA, mature llama.cpp support, and a 2026-09-28 market reading of ~$1,300 (up from ~$1,050 in May). It runs 27B-class models at Q4 comfortably and pairs into 48GB for 70B (see our 48GB build guide).

Mining history is real but mostly overrated as a risk factor for this card: 3090s that mined ran hot memory. What actually matters is how the seller proves current health:

• A short video of a VRAM stress test (e.g., HWInfo or OCCT memory test) with zero errors
• Memory junction temps under load (repasted cards should hold ~95°C or below)
• No modified BIOS / no missing backplate screws

RTX A6000 48GB — the 70B single-card route

A used A6000 at $2,200–2,800 is the cheapest way to put a single card with 48GB on your desk. Blower cooler, 300W, quiet for a datacenter part, and NVLink if you ever want 96GB. It is four years old — slower per dollar than a 5090 for 27B — but it is the only card in this price class that runs 70B Q4 with real context.

Check the same things as the 3090, plus: some ex-farm A6000s arrive with worn blower bearings — ask for a load video with audio.

CMP 170HX — the mining-card gamble

The CMP 170HX is a 64GB mining card now repurposed for inference, and our board shows why people try: 16 sourced runs, including Qwen3.8-27B at 255.9 tok/s (W4A16). 64GB means 70B Q4 fits on one card for the price of a mid-range consumer GPU — if you accept the caveats:

• No display outputs — it is a second GPU by design; you need another card for display
• No warranty, zero resale floor — treat it as fully depreciated on day one
• Driver quirks — it works on Linux with NVIDIA drivers, but expect fiddling; no GeForce Experience niceties
• Cooling/power — passive or aftermarket coolers vary by seller; check the power connectors

Because we do not track a street price for it yet, run every listing through the red-flag checklist below.

Red-flag checklist (any used GPU)

1. No VRAM stress-test proof → walk away
2. Price far below sold history → likely a scam or a dying card
3. Modified BIOS or obviously reworked PCB → walk away
4. Seller history with zero GPU sales → pay with buyer protection only
5. "Untested, as-is" at a 20% discount → you are buying the risk, not the discount

Where to buy

• eBay with the sold-history filter — the market price is what items actually sold for, not what they are listed at
• Local marketplaces — you can test in person; bring the stress-test checklist
• Homelab / LocalLLaMA communities — sellers usually have benchmark history (and links to prove it)

Before you buy anything, check the value index for current VRAM-per-dollar, and the RTX 3090 vs RTX 5090 head-to-head for real tok/s.

Sources

• DiggTop sourced runs and hardware stats: benchmarks · value index · used-card runs
• Used 3090 ~$1,300 and CMP 170HX ~$1,050 (2026-09-28 snapshot): prices
• Used 3090 market history (May 2026, ~$1,050): Howard Resource Group
• A6000 used $2,200–2,800 / new ~$4,650: SpecPicks

Prices are weekly-snapshot items. Re-check prices before buying.