MIT's PCC ports to various micros, especailly x86, also used b.out that was quite similar to a.out.
That was a cross-compiler, right? If so, I remember going over to MIT-LCS and picking up a copy of the sources for the compiler and the MIT PC/IP implementation. I had to show a copy of my ATT source license to the secretary, who made a copy of a 9track tape for me.She was a hoot: dressed like a punk, and we takled about not working for defense companies. We were then able to build and install various TCP/IP utilities on our PC-AT machines running early Windows releases. This was probably early 1980's. I think the PC/IP code was based on David Clark's upcalls idea[1]. It later became the basis for FTP software, which then died when Microsoft added TCP to windows.