sus_man :
The model is Asus amd 7970 925 mhz.
So my gpu is not enough right, then what gpu should I go out
Thanks for reply
I asked about your specific model of Radeon HD 7970 because I was trying to determine if the card is using AMD's reference clock speeds or if the card is using factory overclocked clock speeds.
Factory overclocked cards may consume a lot more power than AMD reference clocked cards.
It is your Cooler Master GX 750W that is the problem, not your current graphics card. The Cooler Master GX 750W doesn't have sufficient maximum combined +12 Volt continuous current capacity to power your system configuration with both the Radeon R9 280X and Radeon HD 7970.
You need a better PSU.
Total Power Supply Wattage is NOT the crucial factor in determining if a power supply is able to properly power the system!!! Sufficient Total Combined Continuous Power/Current Available on the +12V Rail(s) is the most critical factor.