Question Locking i5-9400F Cores at Max Clock

Jun 14, 2019
Hi all,

First post on Tom's Hardware!

Total CPU n00b here, I have built a gaming PC here and there but have never tinkered with hardware in an attempt to push it past factory-spec performance. I recently purchased an i5-9400F because, despite the fact that my RX 480 8GB GPU could easily handle the textures on Total War: Warhammer 2, my i3-8100 was struggling to deliver stutter-free performance when scrolling the massive world map or during large battles featuring thousands of individual models.

The upgrade has delivered a solid improvement in overall smoothness. However, I've become interested in seeing if I can push the CPU's performance somewhat, mostly out of curiosity and a desire to learn more about tweaking hardware. I'm aware that the i5-9400F has a locked multiplier can cannot be classically overclocked, but I have seen bits and bobs online mentioning the potential to "lock" the cores at their max turbo speed of 4.1GHz.

I have a couple of questions about this. First and foremost, will this actually deliver an appreciable increase in performance over allowing the CPU to simply regulate its own clock as needed? The CPU is not bottlenecking my RX 480 but I am about to make the jump to 1440p gaming and am considering upgrading to a card that could experience some bottlenecking within the next year. My second question is: are most games so much more GPU-reliant that a potential increase in CPU performance from core-locking would not be relevant? My last question is: could locking the cores at max clock increase the operating temperature of the CPU beyond what the relatively cheap stock cooler can safely handle?

Thanks for your help!
As the 8400 was reported to throttle with it's factory cooler under constant gaming loads (and I doubt Intel made extensive cooler improvements for the 9400/9400F) , so, if MCE were an option and successfully enabled on your mainboard (you'll know if it is successful if you see all cores at 4.1 GHz in HWMonitor)...

I'd suspect without a better than factory cooler, you'd likely just be 'throttling at a quicker pace'...
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