Test case with GTX 1080 and i5 9600K processor
Test case with GTX 1080 and i5 9600K processor
BF5 begins at 4:34 (or the link directs there), showing a 1-8 fps gap across 1000MHz variations. Occasionally, 2400 delivers higher FPS within measurement limits. The actual difference is just about 5 fps with an RTX 2070. This isn't the root of the OP's issue.
Looks quite quiet at 1080p medium-high, but aren't you hoping more from your 9600K? What are your memory configurations and overall setup? You might want to try running it at 2666. Also, check inspectre for games that could help with CPU cache performance—just a thought. You're safe from any HT issues, so it's likely you're not handling sensitive files or virtual machines while gaming.
You're asking about how your system performs with different settings. It looks like you're comparing your setup to others, especially noting that your 1080 and 9600k running BF5 at medium to high settings gives you around 67-90 FPS on 50-90gps normal. Your friends' builds with an i5 2500k and RX 570 get 50-60 FPS on high settings, which is lower. Your system with 8GB DDR3 RAM seems to handle it better than theirs.
It appears the performance isn’t as high as expected with those specs. Running GTA V at high settings on an 1070 & i5 8400 with 2133mhz RAM usually caps around 100fps. The issue could be related to driver problems—trying a fresh install of the video card drivers might help.
I believe my GPU is failing, so I should just purchase another one. It’s happened before at PC World when I used an RX570 and got 60-70 FPS in ultra settings for BF5.