UNIX, designed and developed on the PDP-11, had similar per-process instruction/data space limitations until V6 and V7 were ported to 32-bit minis ca. 1977 and 1979, and was further constrained by the PDP-11's limited physical address space: 18-bit 1970–75, 22-bit 1975–, so a quarter of the 8086's and 80286's 20- and 24-bit address spaces, respectively.

As an aside, this reminds me of an amusing early example of a rough-and-ready configure-style script[1] included in the BSD source for the compress(1) utility, used to limit the maximum supported LZW code length based on an estimate of memory that will be available to the process[2].

[1] https://github.com/dspinellis/unix-history-repo/blob/BSD-4_3...

[2] https://github.com/dspinellis/unix-history-repo/blob/BSD-4_3...