Retro Game Mechanics Explained is a great series on retro game console programming. If you ever wanted to know how the cake is baked, this is a great channel.

One of the best series up so far is how to program the SNES system. His 16 part series talks about background effects, lag & blanking, DMA and HDMA, memory mapping, color math, hardware registers, background modes 0-6, and the infamous mode 7. It is one of the better explanations of mode 7 that I have seen (though folks with a more formal background in graphics might explain it with with affine transforms alone)

He also covers individual games and topics such as how the Atari 2600 ‘Raced the beam’, Atari quadrascan, pokemon sprite decompression, Pac-Man arcade’s famous kill screen, Mario’s wrong warp, and many other fun topics.