Classic Calculator Was Reverse Engineered from the Bare Metal
In this technical retrospective (2020), @samizdis shares practical architectural lessons learned from running, scaling, or migrating production software under lean constraints.
Core Principles for Independent Builders:
Defaulting to simpler architectures (such as monolithic frameworks, SQLite, or managed VPS) prevents early engineering bankruptcy.
Evaluating true compute and egress costs reveals that high cloud bills can often be slashed by 80%+ through judicious re-platforming.
Code you write at 2 AM as a solo engineer must be easy to debug six months later without complex microservice dependencies.
Community Debate Themes:
HN engineers debated the tradeoffs between cloud convenience and raw server economics, database indexing strategies, and resisting premature architectural complexity.
CATEGORY Frugal Engineering →
HISTORICAL ERA Pandemic Bubble (2020–2022)
COMMUNITY SCORE ★ 168 points
TOTAL DISCUSSIONS 68 comments
It's not really RPN though. RPN lets you write "2 × (5+4)" as "2 5 4 + ×", but the Sinclair Scientific doesn't support that. It would have needed a stack for that, which wasn't available. Instead each operation simply acts on the previous result. You'd have to use "5 + 4 + 2 ×" instead.
Still very impressive how they managed to accomplish all that using that simple TI chip and only 320 instructions.
The patent https://patentimages.storage.googleapis.com/0d/b2/87/7f219f38ca9899/US3934233.pdf for the chip this calculator was based on (the TMS080x) is a real work of art. If you know how to make a transistor and a seven segment display, you can build yourself a fully working calculator with the information in the patent.
The architecture is truly odd, using 44 bit registers (11 x 4-bit BCD) and 11-bit opcodes. It is more like an electrical abacus than a microcontroller.
Somewhat off-topic, but why does the IEEE (a non-profit) have annoying ads on their site? I'm not using an ad-blocker and as soon as I clicked the link I was bombarded by one big half-page ad and a bunch of other ads that are irrelevant to the content of the article.
I would have thought that their very expensive membership fees and article/publication fees would have covered their operating expenses.
This is a great example of a place where you shouldn't use punc-quote formatting. There is no . key on the calculator, but that's not obvious while you're reading the article.
The UI design of calculators is fascinating. Where do you put the buttons? TI and friends have a randomish layout, let alone the TERRIBLE mobile calculator apps.
(Self-promotion) I always wanted to design a calculator and finally got around to it as a lockdown project - https://ucalc.app