L40S 48GB vs RX 7700 XT 12GB for Local LLMs

The L40S 48GB has about 100% more memory bandwidth (864 vs 432 GB/s). Batch-1 decode tracks bandwidth closely, so a model that fits both cards should decode roughly 100% faster on the L40S 48GB. The L40S 48GB fits more of the catalog at Q4/8K — 39 vs 18 of 61 models (48 vs 12 GB VRAM). Largest model that fits the L40S 48GB but not the RX 7700 XT 12GB: Qwen3-Coder-Next (79.7B). MSRP is $8,000 for the L40S 48GB vs $449 for the RX 7700 XT 12GB. MSRP is a launch list price, not live retail — Amazon prices move; click through for the current price. In the Q4/8K head-to-head below (40 shared models), the L40S 48GB posts the higher tok/s in 33 rows vs 7. Methodology.

Spec comparison

	L40S 48GB	RX 7700 XT 12GB
Vendor	NVIDIA	AMD
VRAM	48 GB	12 GB
Memory type	GDDR6	GDDR6
Memory bandwidth	864 GB/s	432 GB/s
TDP	350 W	245 W
MSRP (list)	$8,000	$449
Buy	Search Amazon (affiliate)	Search 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 40 shared models

Model	Params (B)	L40S 48GB tok/s	L40S 48GB fits	RX 7700 XT 12GB tok/s	RX 7700 XT 12GB fits	Winner
Qwen3-0.6B	0.8	687.3 est.	Yes	343.6 est.	Yes	L40S 48GB
Qwen3-Next-80B-A3B-Instruct	81.3	562.3 est.	No	17.6 est.	No	L40S 48GB
gemma-3-1b-it	1.0	549.8 est.	Yes	274.9 est.	Yes	L40S 48GB
Llama-3.2-1B-Instruct	1.2	458.2 est.	Yes	229.1 est.	Yes	L40S 48GB
Qwen3-1.7B	2.0	274.9 est.	Yes	137.5 est.	Yes	L40S 48GB
Qwen3-30B-A3B	30.5	183.3 est.	Yes	111.6 est.	No	L40S 48GB
Qwen3-Coder-30B-A3B-Instruct	30.5	183.3 est.	Yes	111.6 est.	No	L40S 48GB
GLM-4.7-Flash	31.2	183.3 est.	Yes	107.1 est.	No	L40S 48GB
Qwen3-30B-A3B-Instruct-2507	30.5	183.3 est.	Yes	111.6 est.	No	L40S 48GB
Qwen3-Coder-Next	79.7	183.3 est.	Yes	18.3 est.	No	L40S 48GB
Llama-3.2-3B-Instruct	3.2	171.8 est.	Yes	85.9 est.	Yes	L40S 48GB
gpt-oss-20b	21.5	152.7 est.	Yes	171.1 est.	No	RX 7700 XT 12GB
Phi-4-mini-instruct	3.8	144.7 est.	Yes	72.3 est.	Yes	L40S 48GB
Phi-4-mini-reasoning	3.8	144.7 est.	Yes	72.3 est.	Yes	L40S 48GB
gemma-3-4b-it	4.3	141.0 est.	Yes	70.5 est.	Yes	L40S 48GB

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 48GB	RX 7700 XT 12GB
Catalog models that fit	39 of 61	18 of 61
Largest exclusive fit	Qwen3-Coder-Next (79.7B)	—

L40S 48GB details → · RX 7700 XT 12GB details →