What is bottlenecking?
CPU too weak for GPU: GPU sits idle waiting for CPU (15-20% performance loss). GPU too weak for CPU: CPU sits idle waiting for GPU (rarely happens). Most bottlenecking is CPU-limited.
Rule of thumb: Matching tiers
i5-14600K pairs with RTX 4070 (both $400-500 tier). i7-14700K pairs with RTX 4070 Ti ($600-800 tier). i9-14900K pairs with RTX 4090 ($1800+ tier). AMD Ryzen 7 7700X pairs with RTX 4070. Stay within one tier and you're safe.
Benchmark pairs to avoid
Bad: i5 with RTX 4080 (GPU 50% idle). Bad: i9 with RTX 4060 (CPU 70% idle). Good: i7 with RTX 4070. Good: i9 with RTX 4090. If pairing from different generations: one tier up CPU (newer slower CPU matches older faster GPU).
Real FPS impact
Perfect match: 120 FPS. 10% bottleneck: 108 FPS (noticeable). 20% bottleneck: 96 FPS (significant). 30% bottleneck: 84 FPS (major). Most 'mismatches' are 5-15%: livable.
How to check your system
Run a game benchmark (3DMark, GFXBench). If GPU is 95%+ utilized, CPU is bottleneck. If GPU <80% utilized, GPU is bottleneck (CPU powerful enough). Adjust drivers and overclock for small gains.
Budget recommendation
Allocate 40% CPU, 60% GPU in gaming build. $500 budget: $200 CPU (Ryzen 5), $300 GPU (RTX 4060 Ti). $1000 budget: $400 CPU (i7-14700K), $600 GPU (RTX 4070). Don't overspend on CPU if GPU can't leverage it.