Obsolescence Guaranteed — the group behind the PiDP-8, PiDP-11, PiDP-10 and PiDP-1 replica kits — has published a lengthy essay arguing that the computers we actually use descend from a sideline of computing history, not from ENIAC-style batch mainframes. Their narrative runs from Alan Turing's 1936 universal machine and the 1950 Pilot ACE (which ran at roughly 1 MHz) through the machines that made computing interactive.

The story begins with MIT's Project Whirlwind, started in 1945 as a Navy flight-simulator contract and operational by 1951. Whirlwind had a CRT display, a light pen and direct input — the first computer built to work at human speed while every other machine processed punch-card batches. It packed 12,500 vacuum tubes, drew 150 kW and managed 20,000 operations per second. Along the way Jay Forrester's team invented magnetic core memory, which dominated RAM for two decades. Whirlwind's successor SAGE gave operators light guns to point at radar blips — a direct ancestor of the mouse.

Next came the TX-0 (1955–56), the first fully transistorized computer, with about 3,600 Philco transistors and 64K of 18-bit words of core memory. MIT's Tech Model Railroad Club adopted it, importing the word 'hacker' — originally TMRC slang for an inventive technical prank — into computing. Ken Olsen, who had worked on Whirlwind's memory test computer, directed its construction.

In 1957 Olsen and Harlan Anderson founded Digital Equipment Corporation in a Maynard, Massachusetts mill, with $70,000 from Georges Doriot's American Research and Development Corporation — one of the first VC deals ever. The name deliberately avoided the word 'computer' to not scare investors. The essay also defends Olsen's infamous 1977 quote about home computers: he meant appliance controllers, not PCs — he had a PDP-11 at home himself.

The PDP-1 (announced 1959, $120,000, 4,096 18-bit words, 2,700 transistors, only 54 built) brought the Type 30 display — a converted radar tube — and with it Spacewar! in 1962, written by Steve Russell, Martin Graetz and Wayne Wiitanen: the first digital video game, complete with gravity mechanics and custom switch-box controllers built by Alan Kotok. The PDP-1 also hosted the first public computer music performance (MIT's 1963 Science Open House), the DDT debugger, early time-sharing, and Peter Deutsch's Lisp port that invented the REPL.

The PDP-8 (1965) shrank the architecture to 12 bits, eight instructions and a sub-$20,000 price; over 50,000 were sold. Gordon Bell called it 'the Model T of computing.' Its OS/8 is the direct ancestor of CP/M and thus MS-DOS, and its TSS/8 somehow timeshared four users on 4K words of memory. The essay recounts an 88-year-old engineer who had automated a steel plant with dozens of PDP-8s being shown OS/8 in 2017 — he had thought of the machine as a bulky Arduino and never imagined it could load a chess game.

The PDP-10 (KA10, 1968) was the interactive mainframe: MIT's AI Lab ran ITS on it — no passwords, open to the early ARPANET. It saw the birth of Emacs (Richard Stallman, 1976), MacLisp, Shrdlu, and Mazewar, the first networked multiplayer FPS. Bill Gates and Paul Allen wrote the first Microsoft BASIC on a Harvard PDP-10 using their own 8080 emulator. The first worm, Creeper ('I'm the creeper, catch me if you can!'), and its hunter Reaper also roamed here. Only about 1,500 were sold; DEC killed the line in 1983, cannibalized by the VAX.

The PDP-11 (1970) 'defined normal': 16-bit, orthogonal instruction set, Unibus, scaling from a 4K controller to 8 MB systems — a factor of 2,000. Both x86 and the Motorola 68000 were visibly shaped by it. Unix was ported to a PDP-11/20 by Ken Thompson and Dennis Ritchie in 1970; C was designed for its architecture, which is why array[i] equals *(array + i). Thompson's comment 'You are not expected to understand this' comes from its Unix I/O driver. DEC's own RSX-11M, architected by Dave Cutler, later fed directly into Windows NT. Over 600,000 PDP-11s were sold; the line stayed in production for more than 25 years.

The essay closes with the ARPANET: ARPA's 1968 packet-switching RFP went to BBN, whose IMP (Interface Message Processor, initially a Honeywell DDP-516) was the first purpose-built router. The first four nodes — UCLA, SRI, UC Santa Barbara, Utah — went live in late 1969. Ray Tomlinson invented email in 1971, picking @ because it was on the keyboard and 'made sense.' The October 1972 public demo in Washington, D.C., with 40 terminals reaching 10 sites, made the internet feel inevitable. The authors are now building a replica IMP as part of an ARPANET Reconstruction Project aiming to recreate a surfable 1972–73 network — their planned Whirlwind replica is listed for 2027.

The closing argument is the curio's point: a museum shows you history, but a replica lets you toggle in a bootstrap on a PDP-8 front panel and live it.