Yes. There's 1 8kB instruction segment that implements the overlays. The calls to these routines are bounced through thunks that flips the segment register if needed on the call. Each overlay is limited to 8k. The 2.11BSD kernel has about 70k of overlays these days... and they are all almost full, as is the text segment (which is limited to 56k). They get around this by running the TCP/IP stack in supervisor mode, kinda as a process..  This means the total size of the kernel and data for the kernel is 320k on a machine with a 128k address space :).

I've been looking a lot at that code lately... I'm back to patch 0, but am missing ld.c and ranlib.c in my push to get back to the start since they were augmented between 2.10.1 and 2.11 for the new portable archive format... Once I solve those two, it's off to build testing in simh.

Warner