Xyce alternative: from parallel SPICE to logic you can see
Xyce (pronounced like "spice" with a z) is an open-source (GPL), SPICE-compatible, high-performance analog circuit simulator from Sandia National Laboratories. It is built to solve extremely large circuit problems on large-scale parallel computers, also runs serially on common desktop platforms and in small parallel runs on Unix-like systems, and has been used beyond electronics to study networks such as neural networks and power grids. Sandia offers executables and source code; the latest release on GitHub is 7.10.0 (July 2025). It has no schematic editor of its own, but front ends such as Qucs-S can use it as their simulation engine. Xyce answers "what are the voltages in this huge circuit"; digiwleea answers "how do gates become a computer", in a browser.
What Xyce is good at
SPICE-accurate simulation at a scale ordinary simulators cannot reach, by spreading a circuit across many processors; that is what it was built for at a national laboratory. On a desktop it is a free, actively developed SPICE engine, and through Qucs-S it gets a schematic editor. (digiwleea is an independent project, not affiliated with Sandia National Laboratories.)
How digiwleea is different
digiwleea works at the logic level and in the browser: every wire is 0, 1 or floating, so there are no voltages or waveforms to compute, but every bit of a digital circuit is visible as you build it. You wire NMOS and PMOS transistors as switches into NOT and NAND gates, then build adders, latches, registers, RAM and an 8-bit CPU that runs a stored program, through a 40+ level course where every part is checked against its truth table, with an AI tutor (Wleea). For analog behaviour, use a SPICE engine such as Xyce or ngspice; for learning digital logic, a switch-level simulator is faster to understand.
| Xyce | digiwleea | |
|---|---|---|
| Level | Analog, SPICE-compatible (voltages, currents) | Digital, switch level (0, 1, floating) |
| Scale | Very large circuits on parallel computers | Learning-sized circuits, up to an 8-bit CPU |
| Interface | Netlists (front ends such as Qucs-S add a schematic editor) | Visual editor in the browser |
| Runs on | Common desktop platforms; parallel on Unix-like systems | Any modern browser |
| Price | Free, open source (GPL) | 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.
More comparisons: Electronics and SPICE simulators
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
What is Xyce?
Xyce is an open-source, SPICE-compatible analog circuit simulator from Sandia National Laboratories, designed to simulate extremely large circuits on parallel computers, and also runs on ordinary desktops.
Is Xyce free?
Yes. It is open source under the GNU General Public License, with executables and source code available from Sandia and GitHub.
Does Xyce have a graphical interface?
Xyce itself reads netlists. Qucs-S, a free schematic front end, can use Xyce as one of its simulation engines.