I want to know how to check how the motherboard affects the cpu and graphic card performance, and how does a bad motherboard can bottleneck the whole build? i personally have a amd athlon x4 620 cpu, GIGABYTE GA-MA785GMT-UD2H mobo, a xfx hd 5750 gpu, other pieces are not that important i guess. (this is my first rig that i bought 1 year ago)
thank in advance
Motherboard doesn't make much of a difference on performance.
The main important components which determine the performance are CPU,GPU and RAM.
Your current rig is fine for playing games at resolutions like 1280x1024
Your components would run identically in any motherboard. The more expensive motherboards with overclocking/voltage stability etc are only needed for high-end graphics card and CPU's that you're overclocking.
For games, that CPU won't be stressed much as the graphics card is the bottleneck.
Bottom line is if things are stable then that's great. If you decide you need more performance then get a better graphics card. Either way your motherboard will be just fine.