Ripes alternative: build a processor from transistors up

Ripes is a free, open-source (MIT) visual computer architecture simulator and assembly editor for the RISC-V instruction set. Its README lists what it is for: seeing how machine code runs on a variety of RV32IMC and RV64IMC microarchitectures, how cache designs affect performance, how C and assembly become machine code, and how a processor talks to memory-mapped I/O. It runs on Linux, Windows and macOS, with an experimental version in the browser at ripes.dk, and version 2.3.1 came out on October 28, 2026. Ripes shows a processor's datapath working; digiwleea has you build one, gate by gate.

What Ripes is good at

Watching a real instruction set run on real microarchitectures. You write RISC-V assembly or C, pick a processor model, and step through the program while the processor's datapath diagram animates, and you can see how different cache designs change performance. For a computer organization course built on RISC-V, it is an excellent companion. (digiwleea is an independent project, not affiliated with Ripes or its author.)

How digiwleea is different

In Ripes the processor's blocks are given; in digiwleea you make them. In the browser you build NOT and NAND from CMOS transistors, then adders, an ALU, registers, RAM, a program counter and control logic, and finally an 8-bit CPU that runs a stored program, plus the small assembly language behind it, through a 40+ level course where every part is checked against its truth table, with an AI tutor (Wleea). The machine is far simpler than RISC-V, with no pipeline or caches in the course CPU, but you see every wire of it. The two fit together: build the parts here, then watch a full RISC-V processor in Ripes.

	Ripes	digiwleea
Focus	RISC-V processors, pipelines and caches	Digital logic from transistors to a simple CPU
You work with	Assembly or C on given processor models	Circuits you build, then the assembly behind your CPU
Runs on	Linux, Windows, macOS; experimental browser version	Any modern browser, nothing to install
Datapath	Shown and animated	Built by you, part by part
Price	Free, MIT license	Free lab and Act I; Premium for the full course

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.

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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 Ripes free?

Yes. Ripes is open source under the MIT license, with downloads for Linux, Windows and macOS and an experimental browser version at ripes.dk.

What can you simulate in Ripes?

RISC-V programs (RV32IMC and RV64IMC) on several processor models, plus caches and memory-mapped I/O, with the datapath shown as instructions run.

Can I build my own processor in Ripes?

Ripes provides its processor models rather than having you wire them from gates. To build a processor yourself from transistors and gates up, digiwleea's free browser course leads to an 8-bit CPU that runs a stored program, plus the assembly language behind it.