A few days ago, I upgraded my good and tried desktop PC from i3-3220 with HD 2500 to i7-3770 with HD 4000. While I expected they would be similar, since these are CPUs from the same Ivi Bridge generation, but the new graphics started straining my eyes and nervous system immediately. The whole picture and the text feel less stable. Colors have changed and are not as "warm" as before. The picture is brighter and causes strain in the forefront, the eyeballs, and maybe even in my heart. Thus, my good old CCFL Philips display has suddenly become bad. Its PWM never bothered me, but now it does at the brightness of about 70%.

I tried a couple of different drivers and Ditherig. It's all the same.

Could there be any other causes, like changing from legacy BIOS to UEFI, etc.? I also upgraded RAM and SSD.

It's a pity that I'll have to get back to the old CPU with significantly less power — I'm changing the CPU back tomorrow. Hopefully, the picture is back to normal then.

Now I know by experience that if it works, don't touch it.

I changed CPU back today, and all is back to normal. Still can't believe how a slightly different graphics version can be so different for the eyes and nervous system.

The i7 CPU that I tried was used, of course, but it did not look defective, was fast and responsive.

So HD 2500 is good for me with VGA and CCFL. I also glance from time to time at Samsung 971P connected by DVI, with no strain either.

Ditherig app is running just in case.

    a month later

    Quad43

    I'm able to tolerate upto HD 2500..I was using i5 3470T (dual core)for very long time. Latest of this graphic is i5 3470 quadcore…I am getting severe headache within few minutes of usage with HD4000 and anything above.

      4 days later

      I'm using an HD4000 in my Mac successfully, but I know from experience that changing the OS version (newer) or using a near identical Mac with a different panel manufacturer triggers eye strain.

      Unfortunately you cannot pin the problems we experience down to the GPU alone…

      dev