Question Why is my GPU under the reference clocks?

[Gabrielkenway]

4 months ago I bought a used XFX RX 580 8gb Gts. I checked in the GPUZ and I wondered why the core clocks are so low. Ok some months passed and I finally made a research and saw that the standard core clocks of this card were around 1300mhz to 1450mhz. The difference were so big comparing to my 1150mhz. There is some configuration that has been changed? I want to reach at least 1300mhz. The memory clocks are higher than the average that runs at 2000mhz my gpu runs at 2100mhz. I OC my card to 1200mhz, could I reach 1300mhz in the core clock? and what is the difference between the core clock and the memory clock, what will boost more my performance?

 

[rgd1101]

probably been use for mining, custom bios