Advice on CPU/GPU combination please

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The i5-8400 didn't have much problem with the 1080 Ti. The 2080 Ti is faster. If you're at 1080p you might see some CPU limitations (not a matter of fact, just speculation), If you're at 1080p you probably shouldn't have bought the 2080 Ti, or you should upgrade to 1440p at least. If you're at 1440p or 4K you should be fine with the i5-8400.
The i5-8400 didn't have much problem with the 1080 Ti. The 2080 Ti is faster. If you're at 1080p you might see some CPU limitations (not a matter of fact, just speculation), If you're at 1080p you probably shouldn't have bought the 2080 Ti, or you should upgrade to 1440p at least. If you're at 1440p or 4K you should be fine with the i5-8400.
 
Solution