Working PXE/tftp server.

PC Engine's APU.

Serial console.

On the PXE server, create a directory.

mkdir -p /tftpboot/bios

Download the (latest) BIOS firmware: http://www.pcengines.ch/file/apu_tinycore.tar.bz2

Extract in /tftpboot/bios.

Copy syslinux.cfg to /tftpboot/pxelinux.cfg/default, and edit the file.

SERIAL 0 115200
CONSOLE 0

default tinyCore

ALLOWOPTIONS 0
TIMEOUT 600

LABEL tinyCore
        MENU LABEL ^tinyCore
        KERNEL /bios/vmlinuz  console=ttyS0,115200n8
        append priority=low initrd=/bios/core.gz superuser noswap nodhcp embed nozswap blacklist=

Request IP-Address.

udhcpc -i eth0

Download the BIOS firmware.

tftp -g -r /bios/apu140405.rom pxe.server.host

Upgrade the firmware.

$ flashrom -w apu140405.rom
flashrom v0.9.7-r1711-APU on Linux 3.8.13-tinycore (i686)
flashrom is free software, get the source code at http://www.flashrom.org

Using default programmer "internal".
Calibrating delay loop... OK.
coreboot table found at 0xdffdf000.
Found chipset "AMD SB7x0/SB8x0/SB9x0". Enabling flash write... OK.
Found Macronix flash chip "MX25L1605A/MX25L1606E" (2048 kB, SPI) at physical address 0xffe00000.
Reading old flash chip contents... done.
Erasing and writing flash chip... Erase/write done.

Reboot the APU.

reboot