This is by far my favorite development board I've ever had. So the board contains a total of 18 cores, but 16 of them are located on a separate ASIC and it is called the Epiphany. It is essentially a co-processor with 16-cores and its own instruction set architecture. The other two cores reside on the Xilinx Zynq FPGA and they are ARM processors.
The reason why I love this board so much is because of how much you can learn about building a system from the ground up including custom hardware, drivers, compilers, etc. Everything is open source except for the the Epiphany co-processor itself. The board runs a fork of Ubuntu called Parabuntu which contains drivers that allow the host CPU (ARM Cortex) to communicate with the Epiphany 16-core co-processor. The drivers move data between the host and the co-processor via their eLink protocol. The FPGA contains a synthesized component that handles this and the Linux driver interfaces with it. All of this is open source, so you can see how the driver is written, and even the Verilog hardware description language for the eLink components. Since Parallela doesn't consume all of the logic cells on the FPGA, you can even add your own custom hardware accelerators and synthesize them along with the Parallela components. In fact they have a library called "OH" for open hardware which simplifies creating additional hardware accelerators and there is tutorial on how to do it.
So I love this board because you can see how parts of the hardware are built, the drivers are written, and the GCC compiler was forked to support the Epiphany's custom instruction set. That alone makes this a top notch board; however, I haven't even touched on the secret sauce.
The Epiphany packs 16-cores with its own general purpose computing instruction set. So these cores are not as primitive as a CUDA core on an NVIDIA GPU. They are general purpose just like your Intel / AMD / ARM processor. You can either use C/C++ to compile code for the Epiphany or you can put your hacker hat on write assembly. Or even better, do both and inline the assembly where needed. It also supports Python called ePython by the person who worked on that project.
These cores are general purpose, but the memory model is different compared to your typical dual or quad core Intel chip. The cores are connected via a mesh network which is optimized for write transactions. Each core has its own small chunk of local memory, can access the RAM if needed, and read / write between cores. This memory model is what allows this architecture to scale to 1024 cores with ease, but it also presents a fun challenge for developers. Knowing how many clock cycles a write or read transaction takes between cores makes think differently about how your algorithm should be implemented. Also, each core can run a completely different program which is pretty cool. The host processor simply copies the compiled ELF to the cores you want to run it on and then kicks them off running.
There are also a few libraries available in addition to the eSDK that allow you tackle multi-core programming differently like OpenSHEM (shared memory) and COPRThreads (co-processor threads).
This board is just the best all around, and I hope the community keeps it alive. I know Adapteva didn't hit critical market mass with this board, so Andreas the founder had to take a job at DARPA, but so far the community seems to keep going. Unfortunately we won't see the 1024 core Epiphany for ourselves.
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This thing Rocks!!!
This thing rocks!!! WooHooVery easy to use as a regular linux platform. It really shines when you engage the Epiphany III 16-core chip to do image edge detection, or face recognition, or other advanced computational intense algorithms. SuperComputing for the masses (or just me!).Note: I own two Parallels and six Raspberry Pi s.
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