r9 270 run skyrim darksiders 2 and other games at really low frame rate

spec:
i3 550
4g ram
mobo uses pci-e 1.1 while r9 270 use pci-e 3.0

skyrim without vsync 30-100 fps very unstable
darksiders 2 50-80
tomb raider 30-50 fps

all max out 1920x1080
i think those frames are ridiculously low for r9 270. i know everything other than the gpu is ****ty, but what bottle neck the gpu the most?

I'm no expert but I would think your mobo is causing you to not get the full potential of the card.

Well the 270x is a beefed up version of the 7870, which for me, ran skyrim just fine and dandy. You really should put a full description of your setup in your profile, but just off the top of my head I'm looking at that i3. That's a first gen i3, and if it isn't overclocked I could see it possibly being the issue as skyrim relies far more on the CPU than the GPU in terms of where you will see "bottle necking" occuring.

If it's not overclocked, that is where I would start.

Edit: Those FPS seem completely resonable to me on this setup - skyrim is a very buggy game, so you aren't likely to see liquid smooth playback - particularly when the number of NPCs in the area starts to go up.