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Arc B580 12GB vs RTX 4070 12GB for Local LLMs

The RTX 4070 12GB has about 11% more memory bandwidth (504 vs 456 GB/s). Batch-1 decode tracks bandwidth closely, so a model that fits both cards should decode roughly 11% faster on the RTX 4070 12GB. Both fit the same number of catalog models at Q4/8K (18 of 61; 12 vs 12 GB VRAM). MSRP is $249 for the Arc B580 12GB vs $599 for the RTX 4070 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 4070 12GB posts the higher tok/s in 40 rows vs 0. Methodology.

Spec comparison

Arc B580 12GBRTX 4070 12GB
VendorIntelNVIDIA
VRAM12 GB12 GB
Memory typeGDDR6GDDR6X
Memory bandwidth456 GB/s504 GB/s
TDP190 W200 W
MSRP (list)$249$599
BuySearch Amazon (affiliate)ASUS Dual GeForce RTX 4070 OC 12GB (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)Arc B580 12GB tok/sArc B580 12GB fitsRTX 4070 12GB tok/sRTX 4070 12GB fitsWinner
Qwen3-0.6B0.8362.7 est.Yes400.9 est.YesRTX 4070 12GB
gemma-3-1b-it1.0290.2 est.Yes320.7 est.YesRTX 4070 12GB
Llama-3.2-1B-Instruct1.2241.8 est.Yes267.3 est.YesRTX 4070 12GB
gpt-oss-20b21.5180.6 est.No199.6 est.NoRTX 4070 12GB
Llama-3.2-3B-Instruct3.247.4 measuredYes160.7 measuredYesRTX 4070 12GB
Qwen3-1.7B2.0145.1 est.Yes160.4 est.YesRTX 4070 12GB
Qwen3-30B-A3B30.5117.8 est.No130.2 est.NoRTX 4070 12GB
Qwen3-Coder-30B-A3B-Instruct30.5117.8 est.No130.2 est.NoRTX 4070 12GB
Qwen3-30B-A3B-Instruct-250730.5117.8 est.No130.2 est.NoRTX 4070 12GB
GLM-4.7-Flash31.2113.1 est.No125.0 est.NoRTX 4070 12GB
Phi-4-mini-instruct3.876.4 est.Yes84.4 est.YesRTX 4070 12GB
Phi-4-mini-reasoning3.876.4 est.Yes84.4 est.YesRTX 4070 12GB
gemma-3-4b-it4.374.4 est.Yes82.2 est.YesRTX 4070 12GB
Qwen3-4B-Instruct-25074.072.5 est.Yes80.2 est.YesRTX 4070 12GB
Qwen3-4B-Thinking-25074.072.5 est.Yes80.2 est.YesRTX 4070 12GB

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

Arc B580 12GBRTX 4070 12GB
Catalog models that fit18 of 6118 of 61
Largest exclusive fit——

Arc B580 12GB details → · RTX 4070 12GB details →