| Model & Quantization | VRAM Demand | Dual NVIDIA RTX 5090 | NVIDIA RTX PRO 6000 Blackwell |
|---|---|---|---|
| Meta LLaMA 3.3 70B (Q8_0, 8k) | 81.7 GB | Exceeds 64GB (-17.7GB) | Runs Comfortably (+14.3GB) |
| Meta LLaMA 3.3 70B (Q4_K_M, 128k FP8 KV) | 68.8 GB | Exceeds 64GB (-4.8GB) | Runs Comfortably (+27.2GB) |
| OpenAI gpt-oss 120B (Q4_K_M, 8k) | 71.2 GB | Exceeds VRAM (Needs --n-cpu-moe) | Runs Comfortably (+24.8GB, ~140 tok/s) |
| GLM-4.5-Air 106B (Q4_K_M, 8k) | 65.9 GB | Exceeds 64GB (-1.9GB) | Runs Comfortably (+30.1GB) |
| FLUX.1 [dev] (Full FP16 / BF16) | 39.9 GB | Needs Tensor Split (>32GB/GPU) | Runs Comfortably (+56.1GB Unified) |
Both solutions share Blackwell GB202 silicon with 512-bit GDDR7 controllers and 5th-gen `NVFP4`/`MXFP4` Tensor Cores, diverging radically in memory density, power, and topology. Dual consumer RTX 5090s wire 2GB GDDR7 chips per side (`32GB` each), forcing builders onto high-lane HEDT motherboards with dual 600W `12V-2x6` leads pulling 1,150W–1,200W and requiring twin-slot cooling spacing—while lacking ECC protection and hitting an awkward 64GB boundary just shy of `GLM-4.5-Air 106B` (`65.94 GB`) or `gpt-oss 120B MXFP4` (`66.72 GB`). NVIDIA's RTX PRO 6000 Blackwell upgrades to high-density 3GB clamshell GDDR7 ECC modules on a single 600W workstation board, exposing 96GB in one coherent address space. Zero NCCL all-reduce stalls mean effortless single-GPU vLLM serving, 70B FP8 LoRA training, and unquantized FLUX.1 [dev] FP16 (`39.90 GB`).
Already running Dual RTX 5090s (64GB) and hitting OOM on `gpt-oss 120B` (`71.2 GB`) or `GLM-4.5-Air 106B` (`65.9 GB`)? Pass `--n-cpu-moe 4` in `llama-server` to keep shared attention layers in GDDR7 while spilling minimal cold experts to DDR5, plus `-fa on -ctk q8_0 -ctv q8_0` for long-context 70B runs.
Matched Upgrade: A single 600W RTX PRO 6000 Blackwell drops seamlessly onto a 1200W ATX 3.1 PSU with native 12V-2x6 power, underscoring why Dual RTX 5090 rigs (~1,150W+ GPU draw) force awkward 1600W–2000W electrical upgrades.
1200W ATX 3.1 PSU on Amazon Prime ↗Zero monthly subscriptions, 100% private inference, and unmetered tokens for your homelab or workstation.
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Single-card 96GB ECC VRAM avoids PCIe lane bifurcation, cuts peak GPU wattage from ~1,150W down to 600W, and natively fits 70B Q8_0/FP8 (`81.7 GB`), 128k 70B Q4 (`68.8 GB`), and `gpt-oss 120B` (`71.2 GB`) without slow CPU offloading.
No. Two RTX 5090s pull 1,150W–1,200W combined before accounting for your CPU, NVMe array, and microsecond load spikes; dual-5090 towers need 1600W+ supplies on dedicated 20A circuits, whereas one 600W RTX PRO 6000 runs effortlessly on 1200W.
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