What mainboard for around 3 or 4 VGA support? If I have more fund, I plan to buy more VGA. Is PSU 600 watt enough to run 4 VGAs? How about electricity consumed, is 4 VGAs consume four times electricity than one VGA only? Thanks.
To help you understand, what you refer to as "mainboard" is most commonly called a "motherboard." Usually when mining, you will need a motherboard with the most number of PCIE slots because this determines the number of GPUs you can add ("VGAs" are also reffered to here as "GPUs" or Graphical Processing Units).
With regards to your query on PSU, it will depend on the power consumption of your PSU. For example some GPUs consume 150w, so if you want to have 4 of this, 150w x 4 = 600W. You will need a PSU that is more than 600W because you still need to make sure you have extra capacity to handle the CPU, motherboard, storage, etc. It is best to spare at least 20% extra capacity on your PSU.