The DSP-1, DSP-2, DSP-3, and DSP-4 enhancement chips were the same kinds of 8MHz NEC µPD77C25 math co-processors used by English astrophysicist Stephen Hawking's speech synthesizer, which was developed in 1986 after complications of ALS forced him to undergo a tracheotomy, rendering him mute. Because of this shared technology, when the hardware for Hawking's synthesizer started failing in 2017, the original developers were able to create a software version of it by borrowing code from the SNES emulator higan.