One of the reasons why they used Scheme for MIT's 6.001 is because it was an obscure programming language. At the time, some incoming MIT freshmen were likely t

One of the reasons why they used Scheme for MIT's 6.001 is because it was an obscure programming language. At the time, some incoming MIT freshmen were likely to have faffed about with computers in high school or before, learning languages such as BASIC or Pascal. Others would have had little to no computer exposure before entering university. Scheme, being a Lisp and having semantics that were quite different from BASIC, Pascal, or any other language such students were likely to encounter, allowed all students to begin on a more or less equal footing because the programming language used for pedagogy would have been equally unfamiliar to all of them. Obscure CPUs have the same advantage. Plus with careful choice of architecture, or simply inventing your own, you make pedagogy much simpler because the architecture doesn't have all the complicated bits like branch predictors, register windows, speculative execution, etc. that modern CPUs have and you can focus on the basic, "must-have" components.