MBL4 was the first PC based processor.Development started in 2000 and the first release was in December 2001.
The code MBL4 uses is mainly 16bit. It usesthe the MMX instuction set of Intel & AMD CPUs.The 16bit code gave a poor dynamic range - it sounded hissy.
MBL4 is no longer being developed and is released as freeware.