So I was trying Unreal 1 for the first time yesterday. My system is an Athlon XP with 768 MB RAM and Voodoo 3 2000 PCI + FX 5900 XT AGP. The optical Logitech mouse is connected over PS/2. The display is a iiyama 17" CRT. It dual boots Windows 98 SE (Direct X 6.0a, VIA 4in1 4.43, unofficial USB 3.6e patch, PATCHMEM applied) and Windows XP SP3 (DirectX 9.0c, no patches).

Basically, regardless of the video card I use, I get not too bad but still very noticeable input lag in Windows 98 even at the lowest resolution and graphics settings (and anyway the FX 5900 XT is overkill for this game, but the problem also exists with the Voodoo 3). Whereas in Windows XP, there is no input lag at all; the screen refreshes perfecrly in sync with the mouse, even at 60 Hz. Is it because newer DirectX versions improved the input lag in some way? This is really puzzling to me.