Multi-GPU fine-tuning and 70B inference (Q4)
Custom Dual RTX 4090 Training Workstation
Custom Build · Verified 2026-07-23
From $6,500
48GB combined VRAM for 33B-70B models with tensor parallelism. Best value multi-GPU CUDA rig.
Main limitation: No NVLink on RTX 4090; PCIe bandwidth limits multi-GPU scaling. DIY warranty risk.
Some links are affiliate links. We may earn a commission at no extra cost to you. Full disclosure.
Key Specifications
| Specification | Value |
|---|---|
| Form Factor | desktop tower |
| GPU | NVIDIA GeForce RTX 4090 |
| GPU Count | 2 |
| VRAM per GPU | 24 |
| Total Accelerator Memory | 48 |
| Memory Architecture | dedicated VRAM (GDDR6X) |
| GPU Memory Type | GDDR6X |
| Memory Bandwidth (per GPU) | 1008 |
| System RAM | 128 |
| RAM Type | DDR5-5200 ECC |
| Max System RAM | 768 |
| CPU | AMD Ryzen Threadripper 7980X |
| CPU Cores | 64 |
| CPU TDP | 350 |
| Primary Storage | 4096 |
| Storage Type | NVMe SSD (PCIe 5.0) |
| PCIe Generation | PCIe 5.0 |
| PCIe x16 Slots | 2 |
| NVLink Support | No (RTX 4090 does not support NVLink) |
| Power Supply | 1600 |
| Est. Peak Power | 1200 |
| Cooling | custom water cooling recommended |
| Dimensions | Full-tower E-ATX |
| OS | Linux (Ubuntu 24.04) |
| Linux Support | Yes |
| Windows Support | Yes |
| WSL Support | Yes |
| CUDA Support | Yes |
| Metal Support | No |
| Warranty | Varies by component |
| Onsite Support | No |
| Release Year | 2024 |
What Models Can It Run?
Calculated estimates using weight-only memory analysis at Q4 (4-bit) quantization. Actual requirements vary by framework, context length, and runtime overhead. See methodology.
| Model | Params | Required VRAM (Q4) | Fits in 48GB? |
|---|---|---|---|
| Llama 3.1 8B | 8B | 5.52 GB | ✓ Yes |
| Llama 3.1 70B | 70B | 37.14 GB | ✓ Yes |
| Llama 3.2 1B | 1B | 2 GB | ✓ Yes |
| Llama 3.2 3B | 3B | 3.01 GB | ✓ Yes |
| Qwen 2.5 7B | 7B | 5.01 GB | ✓ Yes |
| Qwen 2.5 14B | 14B | 8.53 GB | ✓ Yes |
| Qwen 2.5 32B | 32B | 18.06 GB | ✓ Yes |
| Qwen 2.5 72B | 72B | 38.14 GB | ✓ Yes |
| Mistral 7B | 7B | 5.01 GB | ✓ Yes |
| Mixtral 8x7B | 46.7B | 25.44 GB | ✓ Yes |
| DeepSeek R1 7B | 7B | 5.01 GB | ✓ Yes |
| DeepSeek R1 32B | 32B | 18.06 GB | ✓ Yes |
| DeepSeek R1 70B | 70B | 37.14 GB | ✓ Yes |
| Phi-3 Medium 14B | 14B | 8.53 GB | ✓ Yes |
| Gemma 2 9B | 9B | 6.02 GB | ✓ Yes |
| Gemma 2 27B | 27B | 15.05 GB | ✓ Yes |
| Stable Diffusion XL | 6.6B | 4.81 GB | ✓ Yes |
| Flux.1 Dev | 12B | 7.52 GB | ✓ Yes |
| Flux.1 Schnell | 12B | 7.52 GB | ✓ Yes |
Max model size: 70B class models (~89B params at Q4). These are calculated estimates, not measured results.
Pros & Cons
Pros
- ✓ Good accelerator memory (48GB)
- ✓ Linux support
- ✓ Windows support
Cons
- ✗ No NVLink support (multi-GPU limited to PCIe P2P)
- ✗ No NVLink on RTX 4090; PCIe bandwidth limits multi-GPU scaling. DIY warranty risk.
Compare with Other Workstations
Apple Mac Studio M2 Ultra (192GB)
Apple Mac Studio M2 Ultra (64GB)
ArsenalPC MES2X Dual RTX 5090 AI Workstation
BIZON G3000 G2 (1x RTX 5090)
BIZON G3000 G2 (4x RTX 5090)
BOXX APEXX 8R (1x RTX PRO 6000 Blackwell)
Custom RTX 5090 AI Workstation (Value Build)
Dell Precision 7960 Tower (1x RTX 6000 Ada)
Sources & Verification
Primary source: NVIDIA RTX 4090 Specifications + AMD Threadripper 7980X
https://www.nvidia.com/en-us/geforce/graphics-cards/40-series/rtx-4090/
Verification date: 2026-07-23
Data quality: Vendor specification — from manufacturer datasheet. No hands-on testing was performed.