04. GPU Selection: Mid-Range
The mid-range tier spans $500-$1500 and represents the sweet spot for serious local AI work. These GPUs handle 13B-34B models with reasonable performance.
Recommended Mid-Range GPUs
| GPU | VRAM | Typical Price | Max Models |
|---|---|---|---|
| RTX 4070 | 12GB | $500-600 | 13B FP16 |
| RTX 4070 Ti | 12GB | $700-800 | 13B FP16 |
| RTX 4070 Super | 12GB | $600-700 | 13B FP16 |
| RTX 4080 | 16GB | $900-1100 | 13B FP16 |
| RTX 4080 Super | 16GB | $1000-1200 | 33B INT4 |
| RTX 3090 | 24GB | $800-1000 | 33B FP16 |
Architectural Considerations
The RTX 4000 series (Ada Lovelace) offers 30-40% better performance per watt compared to RTX 3000 series (Ampere). However, the RTX 3090's 24GB VRAM advantage often outweighs architecture efficiency for larger models.
The RTX 4080 at 16GB can comfortably run 13B in FP16 or 33B in INT4. The RTX 3090 at 24GB runs 33B in FP16—useful for developers who need full precision for certain tasks.
Thermal and Power Requirements
| GPU | TDP | Recommended PSU | Fan Noise |
|---|---|---|---|
| RTX 4070 | 220W | 650W | Moderate |
| RTX 4080 | 320W | 750W | Higher |
| RTX 3090 | 350W | 850W | Highest |
Mid-range builds need adequate cooling and power supply. The RTX 4080's dual-slot cooler handles most cases, but the RTX 3090's triple-slot design demands more chassis space.
Real Throughput Numbers
Running Mixtral 8x7B (moe架构) with standard parameters:
- RTX 4080 16GB: 15 tokens/sec, limited by VRAM
- RTX 3090 24GB: 18 tokens/sec, more headroom
- RTX 4070 12GB: Requires INT8, 12 tokens/sec
Calculate whether an RTX 4080 at $999 or an RTX 3090 at $899 offers better value for running Mistral 7B in FP16 precision. Consider VRAM, performance, and power efficiency.