then its not cause when. its strange. I have AMD GPU too and latest 15.7 drivers installed, but haven't seen any problems on both Win7 and Win10 preview...
Also, is there any reason why it's not possible to alter the internal resolution with the DX11ng plugin? Or is it still WIP?
well, mainly its because the way it works. I'll try to explain in short what exactly new gen "NG" renderer have:
so how Dreamcast's (or almost any other) GPU works ? typically in several steps:
1. GPU got textures and geometry need to be rendered.
2. GPU got "start render" signal and do scene draw.
3. rendered picture saved to video memory
.3.1 during storing "picture" can be scaled and/or "flicker-free" deinterlaced in hardware, color data converted to target format with dithering.
4. SH4 CPU can read or write some data to/from rendered picture (so called CPU framebuffer access)
5. one or several frames later memory area from step 3. will be set as source for video output and showed onscreen, with optional another hardware scaling.
I hope this is not too complicated to understood.
but how Dreamcast emulators works ? they just do only steps 1 to 2, so they render picture and immediatelly show it on PC screen, whats all.
DX11NG plugin do all 5 steps. this makes many FB effects possible,
imo best example is "Sega Extreme Sports" - there really great sunspot effects, Vigilante8 also have nice "floating away picture" effect in menus, in "Silent Scope 2" now you can see scope picture at VMU screen (which are part of real picture readed from video memory), and many other games I forgot.
but if we have x10 picture rendered how we can save it to (virtual) GPU's video memory ? we can't, picture is too big, memory is too small.. so saved picture must be exactly that size it was programmed.
but yes, there is known complex methods exists, which makes possible to use together "real" framebuffer and scaled picture, but well, they are complex and not easy to implement. so I don't think this happens in near future...