Also there have been FPGA boards for the Pi before and the BeagleBoard. ModMyPi used to sell the BeagleBoard one, but it no longer seems to be listed and I can't remember what it's name was now.
I nearly bought a BB and the FPGA board for a project, but it seemed that you could only bash a byte at a time between the two processors. If I ever find an FPGA dev board that shares RAM with a "regular" CPU (ARM/Intel), I'd love it.
Biting the hand that feeds IT
