A field-programmable gate array (FPGA) is a type of microchip that can reconfigure itself after it has been manufactured, hence "field-programmable". The technology has found use in emulation as it can reimplement the hardware without having to resort to any kind of binary translation to a computer platform's native code. Instead of adhering to an instruction set or a programming language, FPGA chips are instead programmed using a hardware descriptor language (HDL) that describes the components and logic needed to run the software. This programming isn't permanent; corrections and other changes can be made afterwards so that it isn't limited to one application like an ASIC.
Despite what one may think, FPGAs are not a new technology; they've been around for as long as Macintoshes have been, with manufacturer Altera being the first to introduce an FPGA to the market in 1984. While they already had use in aftermarket cartridges (like setting up mappers for ROMs like the SD2SNES does), using them in place of entire consoles was considered esoteric until commercial devices using FPGAs were released in the mid to late 2010s.
List of aftermarket reimplementations
|Super Nt||Analogue||Super Nintendo Entertainment System||$189|
|Nt Mini||Analogue||Nintendo Entertainment System||$449/$499|
|AVS||retroUSB||Nintendo Entertainment System||$185|