Question about DirectX9 and DirectX10


Jun 4, 2011
To start with, I have these specs:

Intel Core 2 Duo E6420@2.13ghz
Sapphire HD5450 1GB
4GB Ram
Windows 7 Ultimate 64 bit

I have games like Crysis 2, Crysis Warhead, Assassins Creed Brotherhood, Far Cry 2.

I noticed with Far Cry 2 I set the DirectX version to "9". The whole game's lag disappeared, even in high settings. So I googled "How to play games in DirectX9" and came up with these results: You have to run your game's compatibility to Windows XP Service 3 or Service 2 or whatever older compatibility.

Assassin's Creed:Brotherhood>Right click>Properties>Compatibility>Run
this program in compatibility mode for:Windows XP Service Pack 3

So I did it to my other games and Assassin's Creed Brotherhood's lag disappeared even with high settings. The same with Crysis Warhead..

My question is,
Does switching your game's compatibility really sets it to DirectX9?

I want lag free gaming, that's all I want