http://bugs.winehq.org/show_bug.cgi?id=16816
Summary: Fallout 3 slowdowns dramatically when using VATS Product: Wine Version: 1.1.12 Platform: All OS/Version: All Status: UNCONFIRMED Severity: normal Priority: P2 Component: directx-d3d AssignedTo: wine-bugs@winehq.org ReportedBy: ape3000@gmail.com
Seems like dialogs and hit animation from combat resolved using VATS dramaticaly decrease your FPS.
It has been reported that FPS slowdowns in VATS are only occurred with nVidia GeForce 7XXX or older, If you have nVidia GeForce 8XXX, 9XXX or even newer it should work better.
It has been suggested that special shader replacements(smb30->smb20) for older cards could help as the new shaders seem to be mostly involved in vats and dialog sequences...
I think the game works flawlessly on the native windows system also on the older cards (GeForce 7XXX and older), so this is a bug in Wine.