Difference between Directx 9 and 9ex?

[Seyes]

topic pretty much sums it up lol... i just want to know why my auto settings chose the 9ex?

[ayashi]

Necroing this thread because I'm wondering the exact same thing and cannot seem to find another thread discussing it. FORGIVES PLZ I NECRO NOT TO TROLL.

[Drake]

9ex is an enhanced version of Direct3D 9 (it's essentially made for compatibility if you are using a more recent system than windows XP). If your card can't run DX11 and you have 9ex installed, it will try to use it instead of the regular Dx9.

[ayashi]

Nice! Thank you for the prompt answer--I get a slight FPS increase in 9ex after a bit of testing but maybe it's placebo, still, thanks for the info :D

[Phobos]

Google it?
https://www.reddit.com/r/sto/comments/52dggh/direct3d_11_vs_direct3d_9_vs_direct3d_9_ex_halp/?st=j0g8r0j8&sh=12915192

Direct3D 9ex is an extended version of 9 that incorporates a number of advancements designed for Direct3D 10 (namely, better compatibility with certain features included in Vista and later versions of Windows), but may or may not provide any perceptible difference.
Direct3D 11 adds on further compatibility for new features, the most obvious of which are not yet fully taken advantage of by STO.
Direct3D 9 or 9ex will be fine for now, but that shiny new lighting update that's coming soon will require you to run the game in Direct3D 11 mode if you want the full benefit.

[The_Driver]

Or look at the patchnotes of the version that introduced it:

We now use D3D9 Ex mode on Windows Vista and above which substantially improves memory usage and game window resize speed under DirectX 9.

http://pathofexile.gamepedia.com/Version_2.4.2