The Forth Deck mini: a portable Forth computer with a discrete CPU

Original Article ↗ Hacker News Discussion ↗

Enthusiasm for the Forth Deck mini & discrete CPU

  • Many are delighted by a hand‑built Forth machine with a discrete, microcoded CPU.
  • The minimal ALU (single‑bit NOR, multi‑cycle 8‑bit ops) and tiny chip count are praised as elegant engineering.
  • People see it as a fun, educational platform for playing with algorithms, games, and small tools directly on hardware.

“AlphaSmart for programmers” / Model 100 successors

  • Several want a modern, distraction‑free portable like an AlphaSmart or TRS‑80 Model 100:
    • Real keyboard, low‑power reflective display, long battery life, no internet.
  • The Model 100 is repeatedly cited as near‑ideal: great keyboard, ROM tools, AA batteries; main complaints are tiny 8‑line display and clunky data transfer.
  • Some propose a $200 modern unit; BOM constraints (especially display cost) are discussed.

Ultra‑low‑power “zorzpad” and longevity goals

  • A related project aims at a solar‑powered, batteryless notebook (zorzpad) with:
    • Sub‑milliwatt consumption, 53‑year design life, no charging ports, no commodity key switches.
  • Emphasis is on survivability without industrial supply chains: no replace‑often batteries, minimal moving parts, heavy use of redundancy and potting.

Displays: e‑ink vs memory‑in‑pixel LCD

  • E‑ink is seen as attractive but probably too power‑hungry and slow for continuous editing on microwatt budgets.
  • Sharp memory‑in‑pixel monochrome LCDs are championed:
    • True bistability, ~100 µW level, fast refresh, good sunlight readability.
  • Proposals for hybrid designs (small “live” LCD line + large e‑ink page) are compared; memory LCD is argued to be superior overall except for grayscale and size.

Batteries, energy storage, and reliability

  • Strong criticism of batteries for ultra‑long‑life devices:
    • Limited shelf life (~10 years), frequent failures (swelling, leaks, thermal issues), and dependence on future markets.
  • Others suggest using standard, easily replaced cells (AA/AAA/coin) to gain practicality.
  • Alternatives discussed:
    • Supercaps with careful derating and encapsulation.
    • Mechanical or pneumatic charging (pull‑string, bike pump, compressed air) as external, replaceable modules.

Programming models: Forth, UXN/Varvara, CHIP‑8, Lisps

  • Forth is valued for interactivity and bootstrapping, but many find it hard to read at scale.
  • UXN/Varvara gets praise as a frugal, portable VM with a growing, self‑hosting ecosystem, but:
    • Critics argue it’s CPU‑inefficient (interpretive overhead ~20×), limited to 64K RAM, and unfriendly for complex, data‑heavy tasks (e.g., Norvig‑style spell corrector).
    • Varvara’s 2‑bit planar graphics don’t match 1‑bit memory LCDs well; full GUI at 60 Hz is seen as incompatible with ultra‑low‑power goals.
  • CHIP‑8/Octo are noted as fun but IO‑poor and community‑fragmented.
  • There is an extended side discussion on Lisp vs Python:
    • Trade‑offs between flexibility, readability, dynamic typing, and collaboration; Lisp seen as powerful but socially and technically challenging for large shared codebases.

Other hardware & prior art

  • References to:
    • AlphaSmart, TRS‑80 Model 100, Psion 5, Oric‑1, Jupiter Ace, Open Firmware machines, OLPC XO, GEOS on C64.
    • Modern ESP32 devices: M5Stack Cardputer, Devterm, meshtastic boards; some already have Forth ports.
    • Commercial “distraction‑free writers” (e.g., Freewrite) viewed as too expensive or ergonomically off.

Design trade‑offs & UX

  • Debates over GUI vs pure text:
    • Argument that with modern low‑power MCUs and reflective LCDs, efficient GUIs are feasible even under 1 mW; historical “text is cheaper” assumptions may no longer hold.
  • Text editors:
    • Benchmarks show wide power gaps: ultra‑minimal editors can be ~1000× more instruction‑efficient than feature‑rich IDEs.
    • Discussion on designing new editors specifically for tiny, slow, 1‑bit screens, including block editors, single‑symbol views, and strategies to minimize screen updates.