Features
Professional tooling for the MCS-4 microcomputer family and 4004-class CPU simulation in one integrated laboratory.
For a compact overview of the full MCS‑4 lab and Intel 4004 system model (not CPU-only), see Intel 4004 Emulator & MCS‑4 Laboratory (Windows).
If you care about the BASIC → 4004 ASM angle (transpiler, nibble limits, PRINT devices, MCS‑4 PEEK/POKE), read the QuadBasic transpiler overview.
The world's first microprocessor, on a modern workbench. Simulate the Intel MCS-4 system in depth — 4004 CPU, memories, bus, and peripherals — with assembly, debugging, and a high-level language built for 4-bit computing.
What sets it apart
A full MCS-4 system, not a bare CPU
Models the 4004, 4001 ROM, 4002 RAM, 4003 shift registers, and the inter-chip bus, with a realistic default topology (multiple ROM/RAM devices and several 4003s). Ideal for understanding the historic machine as a wired system — not only the instruction repertoire.
Hardware semantics: OR-wired buses
Multiple peripherals on the same port combine the way they do on a wired-OR electrical bus, matching the electrical model. That sets it apart from console-style emulators where I/O does not behave like real hardware.
Peripheral laboratory with saveable profiles
LEDs, virtual printer, LCD, switches, wiring templates, and more — all in profiles you can load when you switch labs or projects. Wire the bench without rebuilding your universe every time.
Test patterns without touching your ROM
Verify wiring and bindings by driving test patterns on outputs from the peripheral panel. Less friction between “is my code wrong?” and “is my binding wrong?”.
QuadBasic: 4-bit BASIC with a transpiler to assembly
A high-level language designed for MCS-4 — nibbles, line numbers, memory and port access — that transpiles to 4004 assembly in the same workbench. A clear bridge between teaching and the metal.
Assembler → ROM image → emulated board
Assemble, program the ROM on the board, and the disassembly reflects the loaded ROM. Visual coherence when ROM and source diverge — with in-app warnings — so you never debug against the wrong image.
Real debugging: breakpoints, stepping, inspectors
Breakpoints by PC address from the disassembler list, single-step execution, pause, and RAM/ROM inspection views. Built for loops and I/O — not just watching the program counter.
Atomic snapshots of the entire machine
Save and restore complete state — CPU, memories, ports, 4003s, bus, metadata — in one gesture. Useful before risky experiments, when reproducing failures, or when comparing before-and-after states.
Speed under control (IPS)
From ultra-slow (seconds per instruction) through real MCS-4 speeds (~46–93 kIPS depending on the cycle model) to maximum throughput for stress tests. Teach, inspect, and hammer the same binary without changing tools.
Organized projects and workspace
Workspace with projects, configurable paths, printer output capture to file, and themes. Less chaos when you alternate between demos, labs, and serious builds.