Praetorian815: For about a week, the game ran at full speed, then it suddenly became slow without me changing anything.
Raze_Larian: If you start a new game, does the performance go back to what it was?
Try the
Windows 8 Performance "Patch" (works in Win 7 and 10, as well).
When you tried different compatibility modes, did you also check 'Override high DPI scaling behavior' and set it to Application, and maybe run as administrator and disable fullscreen optimization (or in Win 7, disable desktop composition and check 'Disable display scaling on high DPI settings')?
WineD3D may work better than Direct3D
http://www.gog.com/forum/divinity_series/windows_8_slow_graphics_problem_fixed_using_wined3d You could try the
4GB Patch to increase the amount of virtual memory that the game (or any 32 bit application) can access in 64 bit versions of Windows.
Are you shutting down all non-essential programs (especially anti-virus) before starting the game?
Try doing a clean boot and then test the game. Click Start, or hit WinKey-R, type in msconfig and hit enter; in the General tab, click Selective Startup, uncheck Load startup items (if required) and leave Load system services and Use original boot configuration options checked. Next, click on the Services tab, check the box to Hide all Microsoft services, then click the Disable All button (maybe make a note of which are currently enabled/disabled), then click OK and reboot the computer.
Run msconfig again to switch back to the normal boot configuration.
It's proving to be a bit difficult to test, unfortunately.
I didn't get another chance to try the game until today, and when I did, it was back to normal speed, even though I didn't do anything aside from restarting my computer once or twice for unrelated reasons. I quit the game and then started it again to see if the problem would come back, but it didn't. This issue seems to be pretty random.
If it happens again, I'll try the stuff you mentioned. I just wanted to let you know that I did read your post. I felt bad about taking so long to reply. It's cool that you guys still personally answer questions about your older games.