Some of the ideas in SPARC came from SOAR, described in David Ungar's thesis [1]. He suggests that the Rice University R2 was the first machine with tags though

Some of the ideas in SPARC came from SOAR, described in David Ungar's thesis [1]. He suggests that the Rice University R2 was the first machine with tags though the R1 [2] seems to have used tags too. [1] https://books.google.co.uk/books/about/The_design_and_evaluation_of_a_high_perf.html?id=gVcZAQAAIAAJ&redir_esc=y https://books.google.co.uk/books/about/The_design_and_evalua... [2] https://en.wikipedia.org/wiki/Rice_Institute_Computer https://en.wikipedia.org/wiki/Rice_Institute_Computer