Your welcome! You can go into the intel control panel and if you put it on 'max performance' under the power tab, your GPU should constantly stay at 1.15ghz as far as the flash games go.. That would also make it idle at 1.15ghz, which is the opposite of what you want. I have a laptop with intel hd 5500 and its always at full speed at idle because i have my power plan on 'Maximum performance'. When your computer is not being used, you can put your power plan to 'power saver' and it should go down to 350mhz. Its not SUPPOSED to drop when on maximum performance. If this started when you upgraded to windows 10, the power plans might have changed because I thought you said you used to have windows 7.
' I just completed my i3 4150+H81M build few days ago, everything is fine but iGPU is idling at 600mhz as opposed to 350mhz, It goes upto 1.15ghz but won't go below 600mhz when doing absolutely nothing. I tried Windows 7 basic theme but it makes no difference ' Let me know if this helps!