RSX-11M+ 2.1, actually (crammed on uPDP-11/23, 64kB (or kw?) memory and a 10MB Seagate

I struggled with them for several years (at work) - rather powerful (for a time), but painfully slow. (I am 44, BTW, and haven't owned a home computer untill recently; the first exposure was on HP-2000, IBM/360 and Univac-1100/42).