There are a few references to the OSF Mach kernel from '98 in a few files, such as https://github.com/apple-oss-distributions/xnu/blob/main/osfmk/ipc/ipc_init.h

There are a few references to the OSF Mach kernel from '98 in a few files, such as https://github.com/apple-oss-distributions/xnu/blob/main/osfmk/ipc/ipc_init.h https://github.com/apple-oss-distributions/xnu/blob/main/osf... EDIT: Apple calls out Mach 3.0. https://developer.apple.com/library/archive/documentation/Darwin/Conceptual/KernelProgramming/Architecture/Architecture.html https://developer.apple.com/library/archive/documentation/Da... https://developer.apple.com/library/archive/documentation/Darwin/Conceptual/KernelProgramming/Mach/Mach.html#//apple_ref/doc/uid/TP30000905-CH209-TPXREF101 https://developer.apple.com/library/archive/documentation/Da... Apple took Mach 3.0 and collapsed it into a single address space for performance purposes. Certainly reasonable.