Bad lag and stuttering in Source Unpack?

Portal
1

When I play the steam release of the game, it runs smooth with no stuttering.

But with the source Unpack, at the same settings, I get stuttering every time I look around, making some chambers much harder than on steam.

Specs:

AMD FX 4300
Nvidia GTX 750 Ti
1TB HDD
8GB Ram

Any ideas?

2

Please post your questions into the helpdesk thread in the future.

3

Try removing “-window -borderless” from the Portal launcher.