Table of Contents

Power Recovery & BIOS Settings

All TetherBoxes are pre-configured to automatically power up after a power cut. If your unit isn't doing this, or you're seeing boot errors, this guide will help you resolve the issue.

Note: This guide applies to the TetherBox Pico, TetherBox Giga, and TetherBox Pro. The entry-level TetherBox (2 and 5 channel) does not have a BIOS.


Symptoms

When BIOS settings are reset, you may experience:

  • The unit does not automatically power up when plugging in the power cable
  • A "Press F1 to Continue" message appears when connecting a monitor
  • Boot errors such as "insert boot media" or "cannot find required map":

EFI Shell error showing

  • "Reboot and Select proper Boot device" error:

Boot device error message


Why Does This Happen?

Cause Description
Depleted CMOS battery The CR2032 button battery inside the unit has gone flat and needs replacing. These batteries typically last 3-7 years depending on usage. Extended periods without mains power drain them faster.
Power issues Frequent power cuts or power surges close together can reset the BIOS configuration.
Failed system drive If reconfiguring the BIOS doesn't restore operation, the internal drive may have failed. Contact TetherX to purchase a replacement pre-loaded drive.

Configuring Automatic Power-Up

Step 1: Enter the BIOS

  1. Switch your TetherBox off by holding the power button for 5 seconds
  2. Connect a display and USB keyboard to your TetherBox
  3. Switch on and immediately start pressing the Del key (or F2 on some models) until you see the BIOS screen

AMI BIOS Main screen

Note: Your BIOS screen may look different depending on the TetherBox generation.

Step 2: Configure Power Recovery

For AMI BIOS (most TetherBox Pico/Giga units):

  1. Use the arrow keys to navigate to the Chipset tab
  2. Find Restore AC Power Loss
  3. Press Enter and select Power On

AMI BIOS Restore AC Power Loss setting with Power On selected

For Phoenix/Award BIOS (older units):

  1. Navigate to Main tab
  2. Find Halt On
  3. Press Enter and select No Errors

Phoenix AwardBIOS with Halt On set to No Errors

Step 3: Save and Exit

  1. Press F4 (or navigate to Save & Exit tab)
  2. Select Save Changes and Reset
  3. Confirm by selecting Yes

BIOS Save & Exit confirmation dialog

Step 4: Test

  1. Unplug the power cable from the TetherBox
  2. Wait 5 seconds
  3. Plug the power cable back in
  4. The unit should power up automatically

If the unit does not power up automatically, the CMOS battery likely needs replacing - see below.


Fixing Boot Device Errors

If you see "Reboot and Select proper Boot device" or similar errors, the BIOS may have lost the boot device configuration.

Possible causes:

  • Bad connection - Try unplugging and reconnecting the drive cable at both ends
  • Failed drive - Contact Support to purchase a replacement pre-loaded drive
  • Configuration issue - The BIOS lost the boot device setting (common after CMOS battery depletion or power surges)

Reconfiguring the Boot Device

  1. Enter the BIOS (press Del or F2 during startup)
  2. Navigate to the Boot tab

BIOS Boot tab showing Boot Option Priorities

  1. Select Boot Option #1
  2. Choose your internal drive from the list (usually shows as the drive model name)

Boot Option dropdown showing available drives

  1. Go to Save & Exit and select Save Changes and Reset

BIOS Save & Exit menu


CMOS Battery Replacement

If the BIOS settings keep resetting after power loss, the CMOS battery needs replacing.

What You Need

  • CR2032 button battery - Available from most electronics or watch battery retailers

Locating the Battery

The CMOS battery is a silver coin-cell battery on the motherboard. On TetherBox Pico units (Gigabyte BRIX), it's typically located near the centre of the board:

TetherBox Pico internals with CMOS battery circled

Note: On some units, the battery may be on the underside of the motherboard.

Replacement Steps

  1. Power off and unplug the TetherBox
  2. Remove the case screws and open the unit
  3. Locate the CR2032 battery
  4. Carefully remove the old battery (note the orientation - positive side up)
  5. Insert the new battery in the same orientation
  6. Reassemble the unit
  7. Reconfigure the BIOS settings as described above

Tip: CMOS batteries typically last 3-7 years. Units left unpowered for extended periods may drain the battery faster.


Still Having Problems?

If these steps don't resolve your issue, contact TetherX support for assistance.

Last updated: January 29, 2026