1979: dozens of users per unix
2019: dozens of unixes per user
@Felthry well, it was originally unics, so theoretically yes. however, to quote brian kernighan, "no one can remember" the origin of the final spelling unix, so for similar mysterious reasons i will claim that "no one can remember" why i spell the plural as unixes
@chr well I was doing it by analogy with latin nouns ending in -ix or -ex, which pluralize to -ices. See "indices" and "matrices".