A lot of people in this forum say that the the 6500 is better value than the 6400 because it has more 0.5Ghz/500mhz, like the base clock suggests. That is wrong!
The base clock is useless, the Turbo frequency is what matters! These processors are so efficient that even the stock intel cooler is enough for them to be hitting the Turbo frequency pretty much all the time.
Take a closer look at the Turbo frequencies for both processors. Theres turbo for 1,2 and 4 cores.
6400 6500
3.3/3.3/3.1 3.6/3.5/3.3
So the difference between the 2 CPU´s is 200/300mhz 99% of the times.
This is battlefield 1 running on a i5 6400. As you can see, all 4 cores are at 3.1Ghz. If it was the 6500, it would have been 3.3ghz
Now do the math, in modern games youre gonna be utilising 4 cores most of the time. 200mhz is not worth the difference in price between the 2 CPU´s!