[Tiberian Sun] Poor direct3d9 performance on modern AMD Radeon GPUs

[Rampastring]

I had Tiberian Sun running perfectly with a GeForce RTX 3060 Ti and CnC-DDRAW, but I recently upgraded to a Radeon RX 9070 XT and now the game runs extremely poorly (~2 FPS at 1280x720).

Switching the renderer= from auto/direct3d9 to opengl fixes the performance, however that disables the filtering modes set by the d3d9_filter key, which I was using to nearest neighbour / integer upscale the game from 720p to 4K.

Tested on versions 6.3, 7.1 as well as the experimental release - all suffer from the same issue.

[LuKeSt0rm]

Try to set singlecpu=false with v7.1

[Rampastring]

@LuKeSt0rm Setting singlecpu=false seems to allow the game simulation itself to run as fast as normally, but rendering remains sluggish. It's like the game ticks at 60 FPS, but only a few frames are drawn and 90% of them are skipped.