The Odroid XU4 is based on the Samsung Exynos5422 with Cortex-A15 2Ghz and Cortex™-A7 Octa core CPUs. So this has 8 cores of two different flavors. The Cortex-A15 is a high performance 32 bit core and the Cortex-A7 is the good old 32 bit core we know and love from the Beaglebone.
But never mind this board for now. No user manual is publicly available. Supposedly you can negotiate an arrangement and sign an NDA to get it, but reports are that requests of this sort have been denied. Most likely you need to be a corporation and have your lawyers talk to their lawyers.
Or mind it if you want. If you can make do with the linux provided by the board vendor, this could work for you. Do you want 8 cores like this or 4 of the 64 bit cores in the Odroid C2? One thing I don't like about the XU4 is that it has a fan. So unless you need all those cores and the fast A15, go with the C2. The following article has ratings based on the Dhrystone benchmark. It seems to say that the A53 doesn't perform much better than the A7 or A8, but the A15 is a significantly better performer than any of those.
Some notable features:
Direct sales by Hardkernel shows a $46 price.
Buying it from Amazon you pay $70.
Either way, it comes with no eMMC and you buy a separate "eMMC module". these are listed as "accessories" and sell for the following prices:
8GB eMMC Module C2 Android Black $16.50 16GB eMMC Module C2 Android Black $24.50 32GB eMMC Module C2 Android Black $37.50 64GB eMMC Module C2 Android Black $57.50 128GB eMMC Module C2 Android Black $76.50You can order them preloaded with Linux or Android (your choice) for the same price. It is not clear if the 128G module will or will not work on the C2 board. (Not that I care, I would buy the 8G module).
They also sell an eMMC "programming adapter" that looks like it would let you plug a module into an SD card reader. This is inexpensive ($1.50) so definitely get one.
Note the heat sink on the board. They offer a 5 volt 4 amp (!!) power supply, and mention that the device will pull 1.2 amps at least.
Tom's electronics pages / firstname.lastname@example.org