I would say it's probably not a hardware issue. Are the graphics drivers fully up to date?
Yes they are.
And as I said, with windows 7 every single RPG Maker game runs fine.
But if I go to Windows 8.1 every single RPG Maker game runs at 17 - 25 FPS, no matter if high resolution or standard. Many events, or no events. But it only happens in full screen. Deactivated all options in my drivers, still the problem.
If I go in windowed mode, even in Windows 8.1 every singe RPG Maker game runs at 60 FPS. Strangely, at a resolution of 1920x1200 I get in Windows 7 13 FPS and with Windows 8.1 about 20 FPS, but only in windowed, else it get's way more worse like 5 FPS. :/
It could be the steam version, because I only seen this error in the steam community and many having this issue...
The only issue I can think I may have, that the CPU runs pretty fast at 60° C / 140° F, but it happens with standard clock too. The fan of the CPU runs at 100%.
But all in all, if you run it in windowed mode, you get a better performance with Windows 8.1 so I wouldn't recommend to uninstall it.
I will try the Windows 10 RP right now, because I only have a demo version of Windows 8.1 at the moment, not enough cash for a full version. :/
The only thing that may can help, is to update the BIOS of your mainboard / motherboard. But for my Asrock are none available, allready installed the latest, only fixed the reboot issue. :/
I using still HDD, may it has to do with the transfer of this part, but SSD are too expensive, in my oppinion. (\s/)
The issue is your graphics card
Why that?
I think it should be fast enough for RPG Maker, as I said only have it with Windows 8.1, not 7.

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