Hey everyone,

After wrestling with hardware and engine issues for days, I finally got Qwen 3.8 Next running properly on my multi-GPU rig. Thought I’d share the setup journey, benchmarks, and thermal results for anyone trying something similar.

Seeing all the ongoing memes on Reddit about multi-GPU setups turning into absolute space heaters and catching fire, I decided to run some rigorous thermal tests to see for myself.

he Troubleshooting Odyssey

1. PCIe Link Speed Issue: Right after installation, one of the cards dropped to PCIe Gen 1 x16. Spent about 8 hours over two days diagnosing and fixing it.
2. Finding the Right Engine:
* Started with sglang-v100, but kept hitting continuous OOM crashes.
* Someone on Reddit previously suggested the pxa engine, but that threw errors as well.
* Eventually tried 1cat-vllm, spent some time tweaking it, and finally hit a stable run!
3. Configuration:

• Running with TP2 PP3.
• Currently, speculative decoding is limited to speculative=1. Setting it to 2 throws an OOM due to memory constraints (might look into optimizing this later, but for now, it works).

Context & Memory Stats

Plaintext

INFO: Available KV cache memory: 8.78 GiB
INFO: GPU KV cache size: 531,288 tokens
INFO: Maximum concurrency for 262,144 tokens per request: 2.03x

Performance Benchmarks

1. Prompt Processing (Prefill)

|Input Length (Tokens)|Speed (tok/s)|
|:-|:-|
|1,024 (1K)|1,389|
|2,048 (2K)|2,536|
|4,096 (4K)|3,210|
|8,192 (8K)|4,336|
|16,384 (16K)|4,679|
|32,768 (32K)|4,470|
|65,536 (64K)|3,820|
|131,072 (131K)|2,759|

2. Text Generation (MTP Comparison)

|Output Length (Tokens)|Base Speed (No MTP, tok/s)|Optimized Speed (MTP Enabled, tok/s)|
|:-|:-|:-|
|128|22.23|41.34|
|256|22.32|42.48|
|512|22.70|43.04|
|1024|22.86|43.28|
|2048|22.83|43.38|
|Average|22.59|42.70|

MTP nearly doubles generation throughput across the board.

Thermals & Acoustics

People often meme about multi-GPU rigs turning into space heaters or jet engines, so I ran a thorough thermal/stress test:

• Stress Test: Ran gpu-burn continuously for 20 minutes.
• Thermal Equilibrium: Temperatures peaked at 65°C and stabilized right around 64°C.
• Fan Curve: Based on my fan control script, the fans were only running at around 76% at 64°C. The cards stay well under 65°C without even needing full blast.

Pretty happy with how stable, cool, and quiet this system turned out.