Not sure about 128x, but 52x is about the physical limit for the media. It's about the point where discs disintegrate (literally!) in the drive spraying shrapnel everywhere. 128x... lets just say the CD drive wouldn't be there anymore. Nor would anything at about the same level as it.

[ESC], select "Save game", pick a (preferable empty) save slot and save game there, blat the turtle, and continue playing Diamondus