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L40S 48GB vs MI300X 192GB for Local LLMs

The MI300X 192GB has about 513% more memory bandwidth (5,300 vs 864 GB/s). Batch-1 decode tracks bandwidth closely, so a model that fits both cards should decode roughly 513% faster on the MI300X 192GB. The MI300X 192GB fits more of the catalog at Q4/8K — 50 vs 39 of 61 models (192 vs 48 GB VRAM). Largest model that fits the MI300X 192GB but not the L40S 48GB: Qwen3-235B-A22B (235.1B). MSRP is $8,000 for the L40S 48GB vs $15,000 for the MI300X 192GB. MSRP is a launch list price, not live retail — Amazon prices move; click through for the current price. Not retail-shoppable: MI300X 192GB (datacenter-class; cloud rental is the realistic way to use it). In the Q4/8K head-to-head below (50 shared models), the MI300X 192GB posts the higher tok/s in 50 rows vs 0. Methodology.

Spec comparison

L40S 48GBMI300X 192GB
VendorNVIDIAAMD
VRAM48 GB192 GB
Memory typeGDDR6HBM3
Memory bandwidth864 GB/s5,300 GB/s
TDP350 W750 W
MSRP (list)$8,000$15,000
BuySearch Amazon (affiliate)—

MSRP is the launch list price, not live retail. Buy links are Amazon affiliate links — the price after you click is the live price.

Q4 / 8K head-to-head — top 15 of 50 shared models

ModelParams (B)L40S 48GB tok/sL40S 48GB fitsMI300X 192GB tok/sMI300X 192GB fitsWinner
Qwen3-0.6B0.8687.3 est.Yes4215.9 est.YesMI300X 192GB
gemma-3-1b-it1.0549.8 est.Yes3372.7 est.YesMI300X 192GB
Llama-3.2-1B-Instruct1.2458.2 est.Yes2810.6 est.YesMI300X 192GB
Qwen3-1.7B2.0274.9 est.Yes1686.4 est.YesMI300X 192GB
Qwen3-30B-A3B30.5183.3 est.Yes1124.2 est.YesMI300X 192GB
Qwen3-Coder-30B-A3B-Instruct30.5183.3 est.Yes1124.2 est.YesMI300X 192GB
GLM-4.7-Flash31.2183.3 est.Yes1124.2 est.YesMI300X 192GB
Qwen3-30B-A3B-Instruct-250730.5183.3 est.Yes1124.2 est.YesMI300X 192GB
Qwen3-Next-80B-A3B-Instruct81.3562.3 est.No1124.2 est.YesMI300X 192GB
Qwen3-Coder-Next79.7183.3 est.Yes1124.2 est.YesMI300X 192GB
Llama-3.2-3B-Instruct3.2171.8 est.Yes1054.0 est.YesMI300X 192GB
gpt-oss-20b21.5152.7 est.Yes936.9 est.YesMI300X 192GB
Phi-4-mini-instruct3.8144.7 est.Yes887.6 est.YesMI300X 192GB
Phi-4-mini-reasoning3.8144.7 est.Yes887.6 est.YesMI300X 192GB
gemma-3-4b-it4.3141.0 est.Yes864.8 est.YesMI300X 192GB

est. = bandwidth-based estimate; measured = curated real benchmark that overrides the estimate. Fits = weights + KV(8K) + 1 GB overhead ≤ 95% of VRAM.

Fit coverage at Q4 / 8K

L40S 48GBMI300X 192GB
Catalog models that fit39 of 6150 of 61
Largest exclusive fit—Qwen3-235B-A22B (235.1B)

L40S 48GB details → · MI300X 192GB details →