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apu features - theory of operation

Boot menu

It lets selecting boot device (first options) and enter another menus to extended coreboot/seaBIOS features. To enter boot menu press F10 key during boot process.

Example view of boot menu

SeaBIOS (version rel-1.12.1.1-0-g55d345f)

Press F10 key now for boot menu, N for PXE boot
Select boot device:

1. USB MSC Drive Kingston DataTraveler 3.0 PMAP
2. USB MSC Drive Kingston DataTraveler 3.0 PMAP
3. SD card SB16G 15193MiB
4. AHCI/0: SanDisk SSD i110 16GB ATA-9 Hard-Disk (14566 MiBytes)
5. iPXE
6. Payload [setup]
7. Payload [memtest]

t. TPM Configuration

Payload menu

It lets using some coreboot/seaBIOS features. To enter payload menu choose Payload [setup] option in boot menu.

Example view of payload menu

### PC Engines apu2 setup v4.6.13 ###
Boot order - type letter to move device to top.

  a USB 1 / USB 2 SS and HS
  b SDCARD
  c mSATA
  d SATA
  e mPCIe1 SATA1 and SATA2
  f iPXE


  r Restore boot order defaults
  n Network/PXE boot - Currently Enabled
  u USB boot - Currently Enabled
  t Serial console - Currently Enabled
  k Redirect console output to COM2 - Currently Disabled
  o UART C - Currently Enabled
  p UART D - Currently Enabled
  m Force mPCIe2 slot CLK (GPP3 PCIe) - Currently Disabled
  h EHCI0 controller - Currently Enabled
  l Core Performance Boost - Currently Enabled
  w Enable BIOS write protect - Currently Disabled
  x Exit setup without save
  s Save configuration and exit

Hidden security registers menu

It lets writing and reading serial number to security registers of the SPI flash chip. To enter hidden menu type shift + z in payload menu.

PC Engines apu firmware features

  • Reading/Writing Serial number to SPI flash

    This feature lets user write and/or read serial number which is contained in hidden security register. To use it first, go to security registers menu.

NOTE: When writing new serial number, only 9 first characters are taken, even if user gives more.

Watch Video showing how Reading/Writing Serial number to SPI flash feature works.

  • Setting bootorder priority

In boot menu user can freely change bootorder.

Watch Video showing how to change bootorder in Boot menu.

  • Enable/Disable Network/PXE boot and press n for iPXE boot string

This feature lets user Enable/Disable booting from PXE. If it is Enabled then during boot process user can access PXE boot string with n button. Also appropriate boot device should be available in boot menu (e.g. iPXE).

Watch Video showing how to enable/disable PXE boot and how to open PXE boot string.

  • Enable/Disable USB boot

    This feature let user Enable/Disable booting from USB device.

Watch Video showing how to enable/disable USB boot.

  • Disable serial console and enable with S1 button

To Disable serial console type t in payload menu. If it is disabled no data will be displayed in serial output. After changing state to Disabled restoring console can be done only via S1 button.

Watch video showing how to disable serial console with payload menu option and then enable it with S1 button.

  • Redirect console output to COM2

Console output is available via COM1 in default. This feature let user redirect console output to COM2.

NOTE: Changing this option from Disabled to Enabled (or the opposite way) will cause losing current output in terminal. The advice is to open new connection in another terminal window on another COM.

Watch video showing how to redirect console output to COM2.

NOTE: In above example serial connection is redirect to telnet. First, it is opened on 13541 port (COM1). After enabling redirect console to COM2, output is no longer available. New telnet connection is opened on 13542 port (COM2) and console output is available there.

  • Enable/Disable CPU boost

This feature lets user Enable/Disable CPU performance boost. To verify if it works, memory test can be done (in boot menu choose payload[memtest]).

NOTE: Notice how memory transfer speed changes depending on CPU boost enable/disable.

Watch video showing how to enable/disable CPU performance boost and verify it.

  • Enable/Disable UARTC/UARTD

    This feature lets user enable/disable superIO UARTx on GPIO header.

    Watch Video showing how to enable/disable UARTC/UARTD.

  • Enable/Disable mPCIe2 clk

If mPCIe2 clk is enabled then GPP3 PCIe clock (which is attached to apu2 mPCIe2 slot) is always on. It is used when extension card is attached to mPCIe2 slot. If no extension card is attached it is advised to set to Disable.

Watch Video showing how to enable/disable mPCIe2 clk.

  • Enable/Disable EHCI0 controller

    This feature lets user enable/disable EHCI0 controller.

    Watch Video showing how to enable/disable EHCI0 controller.

  • Restore default sortbootorder settings

If user wants to bring back default settings in sortbootorder, it can be restored by typing r in payload menu. It will reset enable/disable features and boot order to defaults.

Watch video showing how to restore settings to its default values.

  • Press F10 button to enter boot menu and boot menu 6s timeout

    During boot performance, press F10 button to enter boot menu.

NOTE: After power on user has 6 seconds to enter boot menu. If no button is pressed then automatically boot is performed.

Watch Video showing how to enter boot menu via F10 button and boot menu 6s timeout feature.

  • Screen refresh during memory test performance

To perform memory test choose Payload [memtest] option in boot menu.

During memory test user can refresh screen if the output in terminal is not available. It happens when serial connection is opened during test performance. Screen refresh can be done by typing l or L.

Watch Video showing how screen refresh during memory test works.

  • TPM SHA1 and SHA256 banks enable/disable

PC Engines apu2 supports TPM module. This feature lets user choose which PCR banks are active.

Watch video showing how to enable/disable SHAx banks in TPM menu.