RTX 3090 24GB vs RX 7700 XT 12GB for Local LLMs

The RTX 3090 24GB has about 117% more memory bandwidth (936 vs 432 GB/s). Batch-1 decode tracks bandwidth closely, so a model that fits both cards should decode roughly 117% faster on the RTX 3090 24GB. The RTX 3090 24GB fits more of the catalog at Q4/8K — 33 vs 18 of 61 models (24 vs 12 GB VRAM). Largest model that fits the RTX 3090 24GB but not the RX 7700 XT 12GB: GLM-4.7-Flash (31.2B). MSRP is $1,499 for the RTX 3090 24GB 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 RTX 3090 24GB posts the higher tok/s in 34 rows vs 6. Methodology.

Spec comparison

	RTX 3090 24GB	RX 7700 XT 12GB
Vendor	NVIDIA	AMD
VRAM	24 GB	12 GB
Memory type	GDDR6X	GDDR6
Memory bandwidth	936 GB/s	432 GB/s
TDP	350 W	245 W
MSRP (list)	$1,499	$449
Buy	MSI GeForce RTX 3090 Ventus 3X 24G OC (affiliate) · More listings	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)	RTX 3090 24GB tok/s	RTX 3090 24GB fits	RX 7700 XT 12GB tok/s	RX 7700 XT 12GB fits	Winner
Qwen3-0.6B	0.8	744.5 est.	Yes	343.6 est.	Yes	RTX 3090 24GB
gemma-3-1b-it	1.0	595.6 est.	Yes	274.9 est.	Yes	RTX 3090 24GB
Llama-3.2-1B-Instruct	1.2	496.4 est.	Yes	229.1 est.	Yes	RTX 3090 24GB
Qwen3-1.7B	2.0	297.8 est.	Yes	137.5 est.	Yes	RTX 3090 24GB
Qwen3-30B-A3B	30.5	198.5 est.	Yes	111.6 est.	No	RTX 3090 24GB
Qwen3-Coder-30B-A3B-Instruct	30.5	198.5 est.	Yes	111.6 est.	No	RTX 3090 24GB
GLM-4.7-Flash	31.2	198.5 est.	Yes	107.1 est.	No	RTX 3090 24GB
Qwen3-30B-A3B-Instruct-2507	30.5	198.5 est.	Yes	111.6 est.	No	RTX 3090 24GB
Llama-3.2-3B-Instruct	3.2	186.1 est.	Yes	85.9 est.	Yes	RTX 3090 24GB
gpt-oss-20b	21.5	161.8 measured	Yes	171.1 est.	No	RX 7700 XT 12GB
Qwen3-Coder-Next	79.7	158.2 est.	No	18.3 est.	No	RTX 3090 24GB
Phi-4-mini-instruct	3.8	156.7 est.	Yes	72.3 est.	Yes	RTX 3090 24GB
Phi-4-mini-reasoning	3.8	156.7 est.	Yes	72.3 est.	Yes	RTX 3090 24GB
gemma-3-4b-it	4.3	152.7 est.	Yes	70.5 est.	Yes	RTX 3090 24GB
Qwen3-Next-80B-A3B-Instruct	81.3	152.3 est.	No	17.6 est.	No	RTX 3090 24GB

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

	RTX 3090 24GB	RX 7700 XT 12GB
Catalog models that fit	33 of 61	18 of 61
Largest exclusive fit	GLM-4.7-Flash (31.2B)	—

RTX 3090 24GB details → · RX 7700 XT 12GB details →