Artesyn COMX-P4080 Installation and Use (August 2014) - Manual (Page 113)

BSP Operations
COMX-P4080 COM Express Module Installation and Use (6806800L20C) 113
 NFSboot
 USBFATboot and USBEXT2boot
 MMCFATboot and MMCEXT2boot
Common device environment variables in U-Boot include the following:
 uart# and consoledev
 ethact and netdev
7.19.1 RAMboot
COMX-P4080 has a U-Boot variable called "ramboot".
setenv bootargs root=/dev/ram rw console=$consoledev,$baudrate
$hwbootargs $othbootargs;tftp $ramdiskaddr $ramdiskfile;tftp
$loadaddr $bootfile;tftp $fdtaddr $fdtfile;bootm $loadaddr
$ramdiskaddr $fdtaddr
"ramboot" will first load RAMDISK, Linux kernel and DTB into RAM through network by TFTP
then boot.
0 - ttyS0
1 - ttyS1
2 - ttyS2
3 - ttyS3