KmilaComparison vs GHDL, ModelSim and Vivado
How is Kmila different from the tools typically used in a digital-design course? This page compares Kmila with GHDL + GTKWave, ModelSim and Vivado, fairly: each of those tools is excellent at what it does, and Kmila does not try to replace them in every scenario. The key difference is the goal: Kmila is built to learn and debug VHDL without hardware, integrating the whole flow into a single cross-platform application.
Comparison table
| Feature | Kmila | GHDL + GTKWave | ModelSim | Vivado |
|---|---|---|---|---|
| Free and open-source | Yes (MIT) | Yes | No (limited free edition) | No (free but proprietary) |
| No FPGA / hardware required | Yes | Yes | Yes | Yes (but AMD/Xilinx-oriented) |
| Editor + simulation + waves integrated | Yes | No (separate tools) | Partial | Yes |
| Cross-platform (incl. mobile) | Yes (Win/mac/Linux/Android/iOS) | Win/mac/Linux | Win/Linux | Win/Linux |
| Runs in the browser | Yes | No | No | No |
| Built-in learning tracks | Yes | No | No | No |
| Visual runtime (LEDs, buttons, displays) | Yes | No | No | No |
| Engine verified against GHDL | Yes (148/148) | — (it is the reference) | — | — |
| Synthesis to bitstream for a physical FPGA | No | No | No | Yes |
| Full VHDL-2008 coverage | Partial | Broad | Broad | Broad |
Tool by tool
GHDL + GTKWave
GHDL is the reference open-source VHDL simulator, very complete and mature; GTKWave is its usual waveform viewer. It is a free, powerful combination, but they are separate command-line tools: you install and configure the compiler, the simulator and the viewer yourself, and there is no integrated editor or interactive runtime. Kmila takes GHDL as its correctness standard: the engine is compared against it automatically, with a result of 148 of 148 identical cases (see Benchmark).
ModelSim
ModelSim (from Siemens/Mentor, today alongside Questa) is an industry-standard VHDL/Verilog simulator, very powerful and with excellent debugging capabilities. Its main barrier in the classroom is licensing: free or student editions are limited, and it runs on Windows/Linux, not on mobile or in the browser. Kmila does not aim to match its professional depth, but to offer a free, portable and integrated alternative for learning.
Vivado
Vivado (from AMD/Xilinx) is a full design suite that goes all the way to real hardware: synthesis, place-and-route and bitstream generation for AMD/Xilinx FPGAs, with its own simulator (XSim). It is the right tool when the goal is to program a physical FPGA of that family. In exchange, it is a heavy install, tied to a hardware ecosystem, and not meant for mobile or the browser. Kmila covers the stage before that: understanding, simulating and debugging a design, and estimating its resources, before (or instead of) taking it to silicon.
When to choose Kmila
Kmila is the best choice when you want to:
- Learn VHDL with lessons, challenges and an execution model explained step by step.
- Simulate and debug without installing a toolchain or owning an FPGA.
- Work on any device, including a tablet or phone, or directly in the browser.
- Visualize behavior with waveforms, a schematic and a virtual-hardware runtime.
- Get a resource estimate across 34 FPGA devices without buying any.
When the final goal is a production bitstream, the natural path is to complement Kmila with Vivado or the corresponding open toolchain. Kmila is honest about its scope: its strength is in teaching and debugging, backed by an engine you can verify.
Kmila is an open-source project (MIT License) developed as Terminal Project TT 2026-B059 at ESCOM, Instituto Politécnico Nacional (IPN), by Ulrich Tamayo Daniel. The public repository will be available soon.