Your choice. If the MB has a header for a fan, use it. Most BIOSs allow control of fan speed either automatically or manually. If you connect it to the PSU, it will run at full RPM all the time.
Your choice. If the MB has a header for a fan, use it. Most BIOSs allow control of fan speed either automatically or manually. If you connect it to the PSU, it will run at full RPM all the time.