Just wanted to put this out there. I am sometimes using Dell Optiplex 3020 small form factor with i3-4130. Recently, I decided to do a small upgrade with additional RAM and a better CPU, i5-4670S. After changing the CPU, around two hours of using the new CPU, I got eye strain, red eyes and burning. Ha ha, go figure… So I went back to the old CPU.
Both CPUs are supposed to be of similar generation, the new one, however has HD 4600, while the old one has HD 4400 graphics.
Anyway, just wanted to put this out there. Maybe someone will stumble upon something like this.