I felt I am very silly. I got a work laptop, personal business PC and Mac Mini. Then my monitor got three sockets, two HDMI ports and a Display Port. I used two HDMI ports for my work laptop and personal business PC. So there is only a display port for my Mac Mini, but my Mac Mini got a HDMI port out. I do not want to waste it. At the end, I bought a HDMI to display port cable. I found that is not working, because the cable is only support only one direction, that is from Display Port Out (Computer) to the monitor with HDMI. We cannot do it another way. Then I found a forum post suggested to have a Display Port to DVI converter, then use the HDMI to DVI cable, to connect your computer to the adapter. Then I found it won't work too. The Display port to DVI adapter is one direction only too. That is to connect the display port out in the computer side. Then I finally admited I cannot convert HDMI to display port montior