RTX 4080 Super 16GB vs RX 7900 XT 20GB for Local LLMs

The RX 7900 XT 20GB has about 9% more memory bandwidth (800 vs 736 GB/s). Batch-1 decode tracks bandwidth closely, so a model that fits both cards should decode roughly 9% faster on the RX 7900 XT 20GB. The RX 7900 XT 20GB fits more of the catalog at Q4/8K — 32 vs 25 of 61 models (20 vs 16 GB VRAM). Largest model that fits the RX 7900 XT 20GB but not the RTX 4080 Super 16GB: GLM-4.7-Flash (31.2B). MSRP is $999 for the RTX 4080 Super 16GB vs $899 for the RX 7900 XT 20GB. 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 (44 shared models), the RX 7900 XT 20GB posts the higher tok/s in 35 rows vs 9. Methodology.

Spec comparison

	RTX 4080 Super 16GB	RX 7900 XT 20GB
Vendor	NVIDIA	AMD
VRAM	16 GB	20 GB
Memory type	GDDR6X	GDDR6
Memory bandwidth	736 GB/s	800 GB/s
TDP	320 W	315 W
MSRP (list)	$999	$899
Buy	ASUS ProArt GeForce RTX 4080 Super 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 44 shared models

Model	Params (B)	RTX 4080 Super 16GB tok/s	RTX 4080 Super 16GB fits	RX 7900 XT 20GB tok/s	RX 7900 XT 20GB fits	Winner
Qwen3-0.6B	0.8	585.5 est.	Yes	636.4 est.	Yes	RX 7900 XT 20GB
gemma-3-1b-it	1.0	468.4 est.	Yes	509.1 est.	Yes	RX 7900 XT 20GB
Llama-3.2-1B-Instruct	1.2	390.3 est.	Yes	424.2 est.	Yes	RX 7900 XT 20GB
Qwen3-30B-A3B	30.5	338.0 est.	No	169.7 est.	Yes	RTX 4080 Super 16GB
Qwen3-Coder-30B-A3B-Instruct	30.5	338.0 est.	No	169.7 est.	Yes	RTX 4080 Super 16GB
Qwen3-30B-A3B-Instruct-2507	30.5	338.0 est.	No	169.7 est.	Yes	RTX 4080 Super 16GB
GLM-4.7-Flash	31.2	324.5 est.	No	169.7 est.	Yes	RTX 4080 Super 16GB
Qwen3-1.7B	2.0	234.2 est.	Yes	254.5 est.	Yes	RX 7900 XT 20GB
gpt-oss-20b	21.5	186.5 measured	Yes	141.4 est.	Yes	RTX 4080 Super 16GB
Llama-3.2-3B-Instruct	3.2	146.4 est.	Yes	131.2 measured	Yes	RTX 4080 Super 16GB
Phi-4-mini-instruct	3.8	123.3 est.	Yes	134.0 est.	Yes	RX 7900 XT 20GB
Phi-4-mini-reasoning	3.8	123.3 est.	Yes	134.0 est.	Yes	RX 7900 XT 20GB
gemma-3-4b-it	4.3	120.1 est.	Yes	130.5 est.	Yes	RX 7900 XT 20GB
Qwen3-4B-Instruct-2507	4.0	117.1 est.	Yes	127.3 est.	Yes	RX 7900 XT 20GB
Qwen3-4B-Thinking-2507	4.0	117.1 est.	Yes	127.3 est.	Yes	RX 7900 XT 20GB

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 4080 Super 16GB	RX 7900 XT 20GB
Catalog models that fit	25 of 61	32 of 61
Largest exclusive fit	—	GLM-4.7-Flash (31.2B)

RTX 4080 Super 16GB details → · RX 7900 XT 20GB details →