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RTX 4070 12GB vs RTX 4090 24GB for Local LLMs

The RTX 4090 24GB has about 100% more memory bandwidth (1,008 vs 504 GB/s). Batch-1 decode tracks bandwidth closely, so a model that fits both cards should decode roughly 100% faster on the RTX 4090 24GB. The RTX 4090 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 4090 24GB but not the RTX 4070 12GB: GLM-4.7-Flash (31.2B). MSRP is $599 for the RTX 4070 12GB vs $1,599 for the RTX 4090 24GB. 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 4090 24GB posts the higher tok/s in 37 rows vs 3. Methodology.

Spec comparison

RTX 4070 12GBRTX 4090 24GB
VendorNVIDIANVIDIA
VRAM12 GB24 GB
Memory typeGDDR6XGDDR6X
Memory bandwidth504 GB/s1,008 GB/s
TDP200 W450 W
MSRP (list)$599$1,599
BuyASUS Dual GeForce RTX 4070 OC 12GB (affiliate) · More listingsGIGABYTE GeForce RTX 4090 Gaming OC 24GB (affiliate) · More listings

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

ModelParams (B)RTX 4070 12GB tok/sRTX 4070 12GB fitsRTX 4090 24GB tok/sRTX 4090 24GB fitsWinner
Qwen3-0.6B0.8400.9 est.Yes801.8 est.YesRTX 4090 24GB
gemma-3-1b-it1.0320.7 est.Yes641.5 est.YesRTX 4090 24GB
Llama-3.2-1B-Instruct1.2267.3 est.Yes534.5 est.YesRTX 4090 24GB
Qwen3-1.7B2.0160.4 est.Yes320.7 est.YesRTX 4090 24GB
gpt-oss-20b21.5199.6 est.No225.2 measuredYesRTX 4090 24GB
Qwen3-30B-A3B30.5130.2 est.No213.8 est.YesRTX 4090 24GB
Qwen3-Coder-30B-A3B-Instruct30.5130.2 est.No213.8 est.YesRTX 4090 24GB
GLM-4.7-Flash31.2125.0 est.No213.8 est.YesRTX 4090 24GB
Qwen3-30B-A3B-Instruct-250730.5130.2 est.No213.8 est.YesRTX 4090 24GB
Llama-3.2-3B-Instruct3.2160.7 measuredYes200.5 est.YesRTX 4090 24GB
Mistral-7B-Instruct-v0.37.244.5 est.Yes183.3 measuredYesRTX 4090 24GB
Qwen3-Coder-Next79.721.3 est.No170.4 est.NoRTX 4090 24GB
Phi-4-mini-instruct3.884.4 est.Yes168.8 est.YesRTX 4090 24GB
Phi-4-mini-reasoning3.884.4 est.Yes168.8 est.YesRTX 4090 24GB
gemma-3-4b-it4.382.2 est.Yes164.5 est.YesRTX 4090 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 4070 12GBRTX 4090 24GB
Catalog models that fit18 of 6133 of 61
Largest exclusive fit—GLM-4.7-Flash (31.2B)

RTX 4070 12GB details → · RTX 4090 24GB details →