sobong

I have a Asrock Q1900-ITX mainboard, nanoboot, DSM5.0 4493 update1, USB work fine, I can use usb tv stick with video station, power consumtion 24W idle, full load 48W. but I have a question, this cpu is 4 core, but my xpenlogy only show 2 core at control panel > Info center, how can I fix the problem? Thanks for help