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Best CPU for price for a 1151LGA socket?

Solution
I7-7700k is the best you can do. Lga1151 only supports skylake and kabylake cpus. The new CoffeeLake lga1151 might as well be called lga1151 v2 as the 8th gen CoffeeLake cpus physically do not fit right, requiring a major custom bios overhaul and still don't get full functionality due to differences in pin allocation. So unless you are willing to change out the motherboard as well as the cpu, you are stuck with 6th and 7th gen.

The i5-6400 was a 3 legged dog of a cpu in a grayhound race. It was tied or beaten in gaming by an i3-6100. The only time it showed any lead vrs the i3 was in situations requiring cpu usage over @80% such as some production software like rendering or compiling etc.

Even a move from skylake 4c/4t to a low end...
I'd say the I5 8400 six core is the best cpu under 200, but you have to change the motherboard as it needs a 300 series 1151 board. From your i5 6400 an i5 7400 if your board bios supports it only gets you a few hundred MHz.

If you could sell your i5 6400, H170 motherboard, and 2133 DDR4 you should be able to take your $200 for cpu i5 8400 and use the money from the original combo to get a B360 or H370 board, and some 2666 DDR4 maybe get 16GB
 


I was thinking of buying a i3-8100, do you think its worth it?
 
I7-7700k is the best you can do. Lga1151 only supports skylake and kabylake cpus. The new CoffeeLake lga1151 might as well be called lga1151 v2 as the 8th gen CoffeeLake cpus physically do not fit right, requiring a major custom bios overhaul and still don't get full functionality due to differences in pin allocation. So unless you are willing to change out the motherboard as well as the cpu, you are stuck with 6th and 7th gen.

The i5-6400 was a 3 legged dog of a cpu in a grayhound race. It was tied or beaten in gaming by an i3-6100. The only time it showed any lead vrs the i3 was in situations requiring cpu usage over @80% such as some production software like rendering or compiling etc.

Even a move from skylake 4c/4t to a low end CoffeeLake 4c/4t isn't going to show much benefit other in the few games that still rely on IPC. A move to an i5 8400 ups the IPC a little more, but more importantly opens up space for multi-thread games. If you also replace the mobo.

As is, the i7-7700k is pretty comparable to an i5-8400 across the boards.
 
Solution


Won't fit in your 100 series board, 8 series cpu needs 300 series motherboard.

You wont get too much better for $200, you should look at $300 cpu. I7 6700 is a sure fit

https://pcpartpicker.com/product/7V7CmG/intel-cpu-bx80662i76700

OEM tend not to update one generation to the next, but if your PC has bios support then the i7 7700 should also work

https://pcpartpicker.com/product/9mRFf7/intel-core-i7-7700-36ghz-quad-core-processor-bx80677i77700

Then you get more MHz 3.4 or 3.6 base clock, 4.0 or 4.2 turbo 4 cores 8 threads over your 2.7 base 3.3 turbo 4 core 4 thread cpu. And then you can sell the i5 6400 to get a little money back, looks like $100 to $120 working used on ebay.

I still like the I5 8400 though, 2.8 base 4.0 turbo, 6 core 6 thread cpu, But it needs at least the motherboard swapped to a 300 series. It could run with 2133 DDR4. Though if you have $200 for a cpu upgrade, I think selling the old cpu mobo and ram could buy you a newer mobo and faster ram if not more of it. Say $100 for the 6400, and $50 for the h170, buy a h370 for $80 on newegg, that leaves 70 towards a ram upgrade. A 16GB 2666 kit is $150

Selling the old cpu $100-$120, h170 $50, and 8GB 2133 ram $50, may get a combo price around $220 plus your $200 cpu upgrade for $400 budget

https://pcpartpicker.com/list/qLzKq4
 

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