After I've installed with Windows 7 x64 Ultimate and GPU Drivers, my PCI Express Bandwidth detected as x8 not x16. Fist time I think this is only "crap". But when I play FarCry2 High(DX10 minimum resolution), No AA, 1440x900; the Benchmark result is under 30FPS. Just for the record. I've play Assassin Creed medium in my new SPEC but the FPS is < 30FPS. My old GPU is Zotac 8600gt 256MB DDR3 with Abit AX78 motherboard. And I can play Assassin Creed With the same Graphics settings average in 30PS.
I've search answer over online forum in my country, and there is an answer to my problem (i think): My GPU is bottle-neck when paired with my Agena Phenom 9500 CPU.
I Don't believe it, so i need to find another answer.
Zotac MCP 750a SLI
Phenom X4 9500 (Agena)
Enlight 400watt PSU.
Point Of View 1GB GTS250.
First suspicion is possibly wrong pci-express slot , looks like there are two. Next look in bios under video/pic-e for parameter settings.
Also lastly it's not uncommon when there is insufficient voltage to see something like this. If the slot is correct, confirmed by manual/booklet and actually trying the other slot. Use cpu-z to confirm your result ( you don't mention what you're source was). Sometimes the connection is the physical slot is not snug, remove card and examine slot carefully for any debree, reinstall and try again. good luck
Did you try disabling the on board video ? Did you select the upper pci-e slot in the bios...... they may run 8x8 even though it says 2 pci-e 16 slots.
The old machine, running xp and DX9 ? Big difference between DX9 and DX10/11. More demanding on your card.
As far as FarCry2 goes, It's a heavy hitter. You'll have to turn your settings down.... first in the games control panel and then in the games settings panel ( ingame ). With the limited ability of that card turning physx all the way down or off would probably help a lot.
You said 8600gt ?...... you could try using that as your physics card.... food for thought.