Resseting Mac Logic Board

Resetting your Mac Pro Logic Board can resolve many of your Mac Pro’s system problems. When resetting the Logic Board there are 3 Mac power management reset switches that you can use to troubleshoot various symptoms:

  • System Management Controller Reset (SMC): Used to address issues related to power.
  • Real Time Clock Reset (RTM): Used to address booting issues.
  • System Reset: Switch used to determine if your Mac can’t consistently boot from a cold start resulting in power supply issues

Resetting the System Management Controller (SMC)

On newer Macs, such as the MacBook, Intel iMac and Mac Pro, the Power Management Unit (PMU) on the logic board is called the System Management Controller, or SMC. Earlier models such as the Power Mac G5 and Power Mac G4 had the Power Management Unit. The SMC is a chip on the logic board that controls all the power functions of your Mac and replaces the function of the PMU. It tells your Mac when to turn off, turn on, wake, sleep and remain idle. It also handles system resets from various commands and controls the fans. Resetting the SMC can resolve issues related to your Mac not starting up, not displaying video from your graphics card, sleep/wake issues and fan noise.

Resetting the SMC does not reset the PRAM (parameter random-access memory) or resolve issues that have rendered your Mac unresponsive; this is usually resolved by restarting your Mac. If your Mac unresponsive follow these steps in order until your issue is resolved:

      1. Force Quit Applications (Option + Command + Escape).
      2. Restart (Control + Command + Power Button).
      3. Force Shut Down (Press the power button down for about 10 seconds).

If your computer still shows signs of the Applications or Finder being unresponsive after you have restarted, then try resetting the SMC. To reset the SMC on a Mac Pro:

      1. From the Apple Menu, select Shut Down. (If your computer is not responding follow the above step 3 to force shut down.)
      2. Unplug all cables from your Mac, including power cord and monitor cord.
      3. Wait 2 minutes.
      4. Plug power cord back in, making sure not to press the power button at the same time.
      5. Reconnect the keyboard and mouse to your Mac.
      6. Press the front Power Button and start up your Mac.

System Management Controller Reset (SMC) on a Mac Pro

An alternate way to reset the SMC:

      1. From the Apple Menu, select Shut Down. (If your computer is not responding follow the above step 3 to force shut down.)
      2. Open and remove the side access panel of your Mac Pro.
      3. Press the SMC_RST switch that is located slightly below and to the right of the row of diagnostic LEDs. Use a nonmetallic, nonconductive object to reset the switch if your fingers are too big.
      4. Replace the side access panel.
      5. Press the power button to restart.

Resetting the Real Time Clock

The Real Time Clock located on the logic board controls the date and time functions of the Mac. If your Mac is experiencing a boot issue, resetting the RTC might resolve the problem.

      1. From the Apple Menu, select Shut Down. (If your computer is not responding follow the above step 3 to force shut down.)
      2. Unplug the AC power cord.
      3. Remove the side door from your Mac Pro and then remove the RTC backup battery for at least 20 seconds. You may need to remove the PCI Express Card to access the battery.

System Reset

The Mac Pro has a system reset switch on the logic board that you can use to restart the system while powering on. The switch can be used to determine if your Mac won’t consistently boot from a cold start has power supply issues. To reset the system:

      1. Start up you Mac.
      2. Using a nylon probe tool or a nonconductive and nonmetallic tool, press the system restart switch located on the upper right-hand corner of the logic board.

If your Mac successfully reboots after you press the switch, try shutting it down and restarting it by pressing the front power button. If the Mac Pro restarts when you press the system restart but not from pressing the front power button, then your power supply may need to be replaced.

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