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.