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RTX 3070 8GB vs RTX 4090D 24GB (China) for Local LLMs

The RTX 4090D 24GB (China) has about 125% more memory bandwidth (1,008 vs 448 GB/s). Batch-1 decode tracks bandwidth closely, so a model that fits both cards should decode roughly 125% faster on the RTX 4090D 24GB (China). The RTX 4090D 24GB (China) fits more of the catalog at Q4/8K — 33 vs 17 of 61 models (24 vs 8 GB VRAM). Largest model that fits the RTX 4090D 24GB (China) but not the RTX 3070 8GB: GLM-4.7-Flash (31.2B). MSRP is $499 for the RTX 3070 8GB vs $1,599 for the RTX 4090D 24GB (China). MSRP is a launch list price, not live retail — Amazon prices move; click through for the current price. Not retail-shoppable: RTX 4090D 24GB (China) (datacenter-class; cloud rental is the realistic way to use it). In the Q4/8K head-to-head below (38 shared models), the RTX 4090D 24GB (China) posts the higher tok/s in 38 rows vs 0. Methodology.

Spec comparison

RTX 3070 8GBRTX 4090D 24GB (China)
VendorNVIDIANVIDIA
VRAM8 GB24 GB
Memory typeGDDR6GDDR6X
Memory bandwidth448 GB/s1,008 GB/s
TDP220 W425 W
MSRP (list)$499$1,599
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 38 shared models

ModelParams (B)RTX 3070 8GB tok/sRTX 3070 8GB fitsRTX 4090D 24GB (China) tok/sRTX 4090D 24GB (China) fitsWinner
Qwen3-0.6B0.8356.4 est.Yes801.8 est.YesRTX 4090D 24GB (China)
gemma-3-1b-it1.0285.1 est.Yes641.5 est.YesRTX 4090D 24GB (China)
Llama-3.2-1B-Instruct1.2237.6 est.Yes534.5 est.YesRTX 4090D 24GB (China)
Qwen3-1.7B2.0142.5 est.Yes320.7 est.YesRTX 4090D 24GB (China)
Qwen3-30B-A3B30.551.4 est.No213.8 est.YesRTX 4090D 24GB (China)
Qwen3-Coder-30B-A3B-Instruct30.551.4 est.No213.8 est.YesRTX 4090D 24GB (China)
GLM-4.7-Flash31.249.4 est.No213.8 est.YesRTX 4090D 24GB (China)
Qwen3-30B-A3B-Instruct-250730.551.4 est.No213.8 est.YesRTX 4090D 24GB (China)
Llama-3.2-3B-Instruct3.289.1 est.Yes200.5 est.YesRTX 4090D 24GB (China)
gpt-oss-20b21.578.9 est.No178.2 est.YesRTX 4090D 24GB (China)
Phi-4-mini-instruct3.875.0 est.Yes168.8 est.YesRTX 4090D 24GB (China)
Phi-4-mini-reasoning3.875.0 est.Yes168.8 est.YesRTX 4090D 24GB (China)
gemma-3-4b-it4.373.1 est.Yes164.5 est.YesRTX 4090D 24GB (China)
Qwen3-4B-Instruct-25074.071.3 est.Yes160.4 est.YesRTX 4090D 24GB (China)
Qwen3-4B-Thinking-25074.071.3 est.Yes160.4 est.YesRTX 4090D 24GB (China)

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 3070 8GBRTX 4090D 24GB (China)
Catalog models that fit17 of 6133 of 61
Largest exclusive fit—GLM-4.7-Flash (31.2B)

RTX 3070 8GB details → · RTX 4090D 24GB (China) details →