Like CPUlator, but you build the CPU you program
CPUlator is a simulator and debugger of a whole computer system (CPU, memory and I/O devices) that runs inside a web browser, built with WebAssembly. It runs Nios II, ARMv7 (a Cortex-A9 model), MIPS32 and RISC-V RV32 programs on generic systems or on models of boards such as the DE1-SoC, with a built-in editor and assembler, single-stepping, breakpoints and watchpoints, register, memory and disassembly views, and simulated devices such as LEDs, switches, VGA, timers and a JTAG UART. Its Nios II simulator was first written in 2016 for use at the University of Toronto. If that is what brought you here, digiwleea is a free, in-browser alternative with a different angle: you build a computer from the transistor up.
What CPUlator is good at
For an assembly language or computer organization lab it is hard to beat: nothing to install, real instruction sets, models of the boards a lab actually uses, and a debugger that shows exactly what each instruction did to the registers and memory. (digiwleea is an independent project, not affiliated with CPUlator.)
How digiwleea is different
CPUlator shows what a real CPU does from the programmer's side; digiwleea shows how a CPU does it from the inside. In digiwleea you build the processor in your browser, starting from CMOS transistors and wiring gates, adders, an ALU, registers, RAM and control logic into an 8-bit CPU in a guided 40+ level course with an AI tutor (Wleea). Then you program it in a small assembly language (LOAD, ADD, SUB, STORE, JMP, JZ, OUT, HALT) and watch each instruction move through the circuit, from the fetch cycle to the control unit. It does not run ARM, MIPS, Nios II or RISC-V code. CPUlator is the better pick for coursework in a real instruction set; digiwleea is the better pick for understanding the hardware underneath it.
| CPUlator | digiwleea | |
|---|---|---|
| Instruction sets | Nios II, ARMv7, MIPS32, RISC-V RV32 | One small 8-bit accumulator ISA |
| You see | Registers, memory, disassembly, devices | Every gate and wire of the CPU |
| The CPU | A model of a real processor | Built by you, from transistors up |
| Runs in | The browser | The browser |
| Learning path | A tool for your course's labs | 40+ level course + theory lessons |
| AI tutor | No | Yes (Wleea) |
No sign-up is needed to start: open the lab and place your first transistor, or read the free theory course. The account (and the AI tutor) are optional.
See for yourself: build a logic gate from transistors in the simulator, then follow the path from sand to an 8-bit CPU.
Open the digiwleea lab →Frequently asked
Is digiwleea a good CPUlator alternative?
Yes, if you want to understand digital logic from the ground up. digiwleea is a free, in-browser simulator with a guided 40+ level course where you build every gate from CMOS transistors and work up to a real 8-bit CPU, with an AI tutor to help.
Is digiwleea free?
The sandbox lab and the first act of the course are free and need no sign-up. An optional account adds the AI tutor and cross-device sync; the full course and expanded AI tutoring are included in the monthly or annual Premium subscription.
Do I need to install anything?
No. digiwleea runs entirely in your browser, on desktop or mobile, and works offline once loaded.