I wrote about MicroCore Labs’ MCL51, a microsequencer-based 8051 processor core, back in June (see “How to stuff a wild FPGA: Quad-core 8051 in a $99 Artix-7 Arty dev board multitasks by driving display, printer, music, and sound”) and now, MicroCore has harnessed four instances of these cores running on an Artix-7 FPGA in lockstep to create an n-modular redundant system. This system can detect a variety of soft errors and rebuilds itself when an error is detected. Each of the four processor modules contains independent voting logic that detects errors, so that the failed module can be removed and possibly rebuilt. Successful rebuilding and rejoining the 4-processor gestalt takes 700μsec. (You can get more details in this Microcore app note.)
Here’s a video of the system in operation with some heavy-handed error injection to demonstrate the error-recovery capability of the design:
MicroCore’s MCL51 processor core consumes only about 300 LUTs, so four instances easily fit in the Artix-7 A35T FPGA on the $99 Digilent ARTY dev board used in the video. This board is a real bargain because it includes a voucher for a device-locked copy of the Xilinx Vivado HL Design Edition, which lists for $2995.