05. GPU Selection: High-End
The high-end tier ($1500+) targets professionals and enthusiasts who need maximum performance or run the largest models locally.
Recommended High-End GPUs
| GPU | VRAM | Price | Use Case |
|---|---|---|---|
| RTX 4090 | 24GB | $1600-1800 | 70B INT4 |
| A100 40GB | 40GB | $3000-5000 | 70B QLoRA |
| A100 80GB | 80GB | $8000-15000 | 70B FP16 |
| H100 | 80GB | $25000+ | Production |
RTX 4090 Deep Analysis
The RTX 4090 dominates the consumer high-end segment. Its 24GB VRAM handles 70B models in INT4 quantization. The 450W FNAW (floating-point operations per watt) efficiency reflects Ada Lovelace's improvements.
Throughput: 21,000 TFLOPS (FP16)
memory_bandwidth: 1,008 GB/s
PCIe: 4.0 x16
Real-world Llama 3 70B INT4 performance: 8-12 tokens/sec on a single RTX 4090. This is interactive but not blazingly fast.
Data Center GPU Considerations
The A100 comes in 40GB and 80GB variants. The 80GB model costs approximately twice as much but is essential for 70B FP16 workloads. A100 cards require dedicated servers with appropriate cooling and power infrastructure.
H100 cards are currently production-tier only—pricing reflects enterprise demand rather than consumer accessibility.
Multi-GPU Scaling
High-end builds often combine multiple GPUs. Scaling efficiency:
| Configuration | Relative Performance | VRAM Pool |
|---|---|---|
| 1x RTX 4090 | 1.0x | 24GB |
| 2x RTX 4090 | 1.7x | 48GB |
| 4x RTX 4090 | 2.8x | 96GB |
Scaling is sub-linear due to communication overhead between GPUs.
Power and Cooling
The RTX 4090 at 450W requires:
- Minimum 850W PSU (1000W recommended)
- Excellent case airflow (30+ CFM front intake)
- ambient temperature under 30°C for sustained operation
Calculate the total system cost (GPU + motherboard + CPU + RAM + PSU + case) for a dual-RTX 4090 build. Research current component prices and sum them.