FPS dropped after changed CPU

ckh997

Prominent
Feb 27, 2017
4
0
510
Hello guys.
It's not my problem, but my friend's.

My friend was using:
i5-760
GTX 950 OC
12GB RAM

for his desktop and running Forza Horizon 3 about 40-50 FPS for average on low setting.
But then he said after he changed his CPU, Forza Horizon 3 was not running as smooth as before.
He said he's keep getting 20s FPS for average after he changed CPU.
It's still on same setting in game.
CPU that he changed was i7-3770.
Rest of the specifications of his desktop are the same but CPU.
I tried that disabling CPU 0 method, and basically every fixes that is currently available, but it's still the same.

Can you guys figure out what is causing this problem and how to fix them?
if you need more info, I can ask him and tell you.
 

ckh997

Prominent
Feb 27, 2017
4
0
510

Well, yeah that's the first thing that he has to do and that's what he did right after changed them.

But then rest of the games are running fine, better than what he normally get when he uses old cpu (i5-760)
CS:GO, Overwatch, Need For Speed, Call of Duty, etc. those are running fine.
The weirdest thing is that the worse performance issue is only occurs on Forza Horizon 3.
 

ckh997

Prominent
Feb 27, 2017
4
0
510


Right, I forgot to mention that...
He did reinstalled windows right after he changed them, and he did it again right after your answers are up.
But, result was same.

As I mentioned above, rest of his games are running fine as it suppose to be.
Problem is only occurring on Forza Horizon 3.
 

ckh997

Prominent
Feb 27, 2017
4
0
510


Thanks for the answer, but negative...
We tried disabling hyperthreading in bios, but the result was same...