Donald Knuth – The Patron Saint of Yak Shaves (2017)
This and more.  The Sail version of TeX is mentioned, but everything else had a usable prototype, too: An early version of Metafont in Sail, an early version of Web (called Doc, though I don’t recall what the names of the Tangle and Weave equivalents were), and an early version of Computer Modern fonts in the early Metafont language.<p>Though fully documented and available via anonymous FTP on the Arpanet, all of these prototypes were experimental proofs-of-concept and were completely discarded, along with the languages they implemented, with the “real” versions rewritten from scratch by Knuth (each first by hand on legal pads, then typed in and debugged as a whole.)<p>And you missed one more obscure but instructive example: To get the camera-ready copy for ACP Vol 2, Knuth purchased an Alphatype CRS phototypesetter. And, unhappy with the manufacturer’s firmware, he rewrote the 8080 code that drives the thing.  Eight simultaneous levels of interrupts coming from various subsystem: the horizontal and vertical step-motors that you had to accelerate just right, while keeping synchronized with four S100 boards that generated slices of each character in realtime from a proprietary outline format, to be flashed into the lens just as it was passing the right spot on the photo paper. (Four identical boards, since you had to fill the second while the first one did its processing; times two for two characters that might overlap due to kerning). Oh, and you had to handle memory management of the font character data since there wasn’t enough RAM for even one job’s worth (see our joint paper).<p>Fun times. I did the driver on the mainframe side, so got to be there for the intense debugging sessions that used only the CRS’s 4x4 hex keypad and 12-character dot-matrix display.<p>Thanks for the DVI shout-out, btw.