Sparkle Arc Pro B60: only 150 GB/s VRAM bandwidth (spec 456)

A Sparkle Arc Pro B60 owner reports the card delivering only 150 GB/s of VRAM bandwidth in clpeak's --global-memory-bandwidth test, against a 456 GB/s specification, and is asking other B60 owners to run the same test to confirm. The owner says dense LLMs run at roughly half the speed of other reports, with Qwen3-27B Q4_K_M reaching 8.6 t/s versus 16 t/s on other B60s using the same llama.cpp build and flags. The discrepancy matters because if the 150 GB/s figure is reproducible, the card's memory bandwidth is about a third of its rated spec and would explain the slower token generation.

I’ve been testing dense LLMs on my B60 and they seem to run at half the speed of some other reports - Qwen3.8-27B Q4 K M at 8.6 t/s, against 16 t/s on other B60s with the same llama.cpp build and flags. Troubleshooting with claude led me to a potential issue with vram bandwidth. Testing with clpeak –global-memory-bandwidth I got the result - 150 GB/s. If another B60 owner can run the same test and let me know I would really appreciate it.