A collection of 21 posts
TL;DR: We rebuilt the 1971 Intel 4004 — the world's first commercial microprocessor — as a genuinely 4-bit CPU inside DigiSim, using ordinary logic blocks: a control unit, program counter,...
In the previous post, we built the D latch: a circuit that accepts a Data input and a Write-enable line, and faithfully stores whatever it sees on Data at the...
The previous post ended with something genuinely new in this series: a circuit that could remember. The R-S latch, built from two cross-coupled gates, held its output even after the...
In the previous post, we saw what happens when feedback chases itself around a loop with no place to land: the output flips, which triggers a flip back, which triggers...
In the previous post, we finished building something that computes: given any three input bits, the full adder works out the correct sum and carry in a single stroke. You...
In the previous post, we built the half adder: XOR for the sum bit, AND for the carry bit. Two inputs in, two outputs out — a clean circuit that...
In the previous post, we built a circuit that chooses — a multiplexer that uses a selector input to steer one of several signals to a single output. Every circuit...
In the previous post, we completed the full set of two-input logic gates — AND, OR, NAND, NOR, XOR, XNOR — each one a different question about its inputs. Every...
In the previous post, we built XOR from relays — the gate that asks are these two inputs different? It lit a lamp precisely when its inputs disagreed. That circuit...
In the previous post in this series, we explored the NOR gate — and one of the most remarkable facts in all of digital logic: NOR is universal. From this...
In the previous post in this series, we built the NAND gate — NOT-AND — and discovered something remarkable: you don't need a full toolkit of different gates to build...
In the previous post in this series, we built the buffer — the gate that restores a signal, regenerates its strength, and copies truth without changing it. Step back and...
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