1) Build yourself (or buy, borrow, whatever if you fancy that) a computer with the following:
CPU: AMD Phenom 9650 x4 @2.3 Ghz
GPU: GTX 470 (1280 MB GDDR5)
RAM: 8 GB RAM
OS: Windows 7 64-bit
2) Go make a mission with some units in it, preferrably in Agia Marina or a big city.
3) Go play, you'll probably notice that doors take their time in responding and the AI is not reacting to anything at all.