Hi, (long explanation)

lately I'm into this never ending adventure optimizing a netbook oriented mini-itx mb based on the old Atom D2x00 dual core and its "old" Powervr SGX545 / GMA36x0 gpu in Windows 8.1.
This iGPU was a features rich low power smartphone oriented architecture and never found peace in the x86/x64 world even in its times with Win7 32bit only drivers, high expectations but low results when not gfx errors that at least were solved in the latest drivers but probably slower than the older GMA9x0 iGPU when running old dx6/7 games (faster in DX9 ones at least). They did update the drivers until late 2013 but who knows which was the real mistery around it for a capable 400Mhz/600Mhz DX10.x gpu/DDR3 system memory; it makes me crazy how it's possible that in Windows 8.1 (forcing the latest drivers) I got 1300 points in 3DMark2000 with latest .1096 drivers, clean installation everything works even the GUI and DXVA acceleration that decode 60fps 1080p H264 videos with 30/40% of cpu utilization without any problems. Others numbers are ironically "faster" 1900 points in 3DMark03, 790 points in 3DMark05. I tested lately a P4 with a G550 and 3DMark2000 gave me 3000 points. Come on, it's impossible. But the rendering is mostly ok, I tried even games like GTA IV and Doom3 and Thief Deadly Shadow they all are rendered ok, only frame rate seems low even with low resolution more than expected.

But more problems come with older dx6 games like Thief2; lately I had some interesting thoughts I'd like to ask you opinions about. The game can run into a modern o.s. with a third party patch that can enable a Directx9 renderer for the game. Interesting thing: with the DX9 option enabled it start and shows artifacts at the menu, impossible to read anything but once I got to enter in a random way into the 3D game, had no errors and MUCH faster fps (but it hanged after a while) than it did with the older DX6 renderer (disabling the dx9 one in the config file) where it run flawless BUT only in windowed mode / sort of fake "borderless fullscreen" and MUCH slower frame rate. The real full screen mode can't start.
This make me think, is it possible than even 3dmark2000 and older games did run but not real full screen mode and that might explain such low frame rates maybe running along with the background GUI? Could it be that modern Win like 7 / 8 or 8.1 with the WDDM driver model, simply needed different drivers and games to work fast in a new way into these "3D-accelerated" GUI?
To make a test I tried installing a Geforce FX 5200 PCI into another config with the fastest Core2 E8600, Win 8.1 too forcing Vista drivers into it as I did with the system above. The card works well both in GUI and games but as suspected 3DMark2000 seems to run as slow as the GMA3600 (first test low detail like 20-35fps)! I suppose the Geforce FX 5200 into a XP system should fly into 3DMark2000 literally.

Now, opinions? Any way to force a real fullscreen isolation in Win8.1 to test if these gpu are not fully running at their best cause older games maybe worked in a different way in older o.s. and when they work into new o.s. they might not "isolate" the Direct3D rendering from the GUI itself not entering into a real full screen?

Thanks for any opinions.