The ODROID-C2 is a 64-bit quad-core single board computer(SBC) that is one of the most cost-effective 64bit development boards available in the ARM world.
SpecsUpdate
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Pros
Pro Good support for Ubuntu
The C2 has pretty decent support for Ubuntu and it can be used with it for basic day-to-day operations such as browsing the web and editing documents with LibreOffice among others.
Pro Superior performance compared with other boards
Pro Built-in heatsink
The ODROID C2 has a built-in heatsink which covers the CPU and two of the RAM chips.
Pro Can fit inside Raspberry Pi cases
Since its shape and size closely mimic that of Pi 3, it can fit on most Raspberry Pi cases available.
Pro Will have mainline kernel support
Pro Relatively low power requirements
The board by itself needs about 0.5A to run, but it's advised to use a 2A power supply for when peripherals are attached.
Cons
Con No built in WiFi
There is no built-in WiFi, and kernel headers for 3.14 are almost impossible to find, making driver compiling very difficult.
Con Old kernel available
Only the 3.14 branche is available
Con Early revisions use a 2.5mm power socket instead of a USB port
Early revisions of the C2 use a 2.5mm power socket instead of the micro USB port available on the board or any of the other USB ports. While not a drawback in terms of strength of the board, it's a bit annoying having to order a new power supply to work with the C2.
Later revisions of the board can use the USB port for charging. However, ODROID recommends using the power socket if there are several devices attached to the board because they can increase the draw up to 2A and a lot of cheaper USB power adapters won't do 2A.
Con Might have problems with default HDMI resolution when first starting up
It's not unusual for the C2 to have a "Mode not supported" message when first booted up and connected to a monitor through the HDMI port. This can be fixed by logging through SSH and editing the boot.ini on a FAT partition on the SD card to set the correct HDMI resolution and the process is detailed pretty well on the ODROID wiki but it may be out of scope for some users and pretty annoying for the rest.