Yamaha Ym2149 sound chip created by MikeJ in VHDL, compatible with Xilinx and Altera.
MikeJ started by implementing the 555 chip in VHDL, used for sound effect (about five different sound) in original Space Invaders arcade game... and then realised this VHDL version of Yamaha Ym2149 sound chip compatible with Amstrad CPC.
Not published, '''YM2149_linmix.vhd''' original version (coming from FPGAmstrad NEXYS4 v0 backup), patched to run in [[FPGAmstrad]] (see "freemac" occurrence in code) :