After following the installation instructions here: https://archlinuxarm.org/platforms/armv7/ti/beaglebone, I am unable to get the BBB to boot Arch from emmc. It boots fine everytime from the microSD card. I have navigated around the file structure on the emmc after expanding the tar, and everything appears to be there.
After poweroff and removing the microSD card, reapplying power results in a hung boot. The Power LED and RJ45 LEDs show their normal indications. USR0 & USR3 remain on solid. No response to ssh login attempts. Poweroff, reinsert the microSD card, reapply power and it boots fine. The BBB is running on the 2A power supply that came with it in the Adafruit starter kit.
BTW, I am new to Arch and BBB both. Recently switched from Kubuntu to Arch on my PC and that went very smoothly.