Steam – Running games in DirectX 6

I'm unsure why you added DXLEVEL 80.

512Mb of RAM is very small; it is clearly the bottle neck in this case.

You do state though that the other noted games run fine. It is possible that with all the content that is in use at the same time when playing TF2 that your RAM is just not capable of holding it all (and TF2 has a lot of content, such as hats).

As for the shown minimum requirement, maybe due to the steady increase in the size of the game since release and all the addition new items/content, the stated requirement is actually no longer realistic.

As of csgo, there are no real configs that could really affect your fps, aside from those in the video settings, so those are the only ones that you can tweak around and test with.

Even the developers said a hardware upgrade is probably the best solution to a low fps problem.

I would say it is purely your graphix card's limit, instead of the game settings.

Hope that helped.