Modelsim is one of the best multi-language HDL simulators developed by Mentor Graphics.
Modelsim is essential for simulation of hardware description languages such as VHDL, Verilog and SystemC. Modelsim also includes a powerful C debugger.
ModelSim can be used independently, or in conjunction with Altera Quartus or Xilinx ISE/Vivado. The HDL simulation can be performed either using the graphical user interface (GUI), or automatically using TCL/TK scripts.
Modelsim runs under a FlexLM license and, as you can imagine, a single license is quite expensive for an end user such as a student or hobbyist.
There is one way to get a legal free Modelsim license:
- From Altera website, downloading Quartus II web edition. Altera provides a free license limited to Altera FPGA. This means you cannot compile technology libraries of ASIC or FPGA such as Xilinx, Microsemi but you can compile and simulate your own RTL code.