What is free software?
Free software are those software that give you the following 4 freedoms:
Freedom to run the program.
Freedom to modify the progam to your needs.
Freedom to redistribute the program.
Freedom to distribute a modified version of the program.
Why use free software?
You can get this question answered from the GNU webpage.
Where do I get this GNU/Linux OS?
There are a number of GNU/Linux distributions you can choose from.
They come along with extensive documentation, on installing and using the operating system. You can download the "ubuntu" version of Linux here : www.ubuntu.com or you can always google for more latest versions of Linux OS.
Electric is complete and sophisticated VLSI design software primarily authored by Steven Rubin. Some of its features includes custom ic layout, design rule checking, network consistency checking, VHDL Compilation, silicon compilation, etc. Read about its technical specifications here.
Alliance is a complete set of CAD tools and libraries for digital VLSI design developed at LIP6 laboratory of the Pierre et Marie Curie University. It includes a VHDL compiler and simulator, logic synthesis t ools, automatic place and route, DRC, extractor, functional abstraction and formal proof tools etc.
Icarus Verilog is a verilog simulation and synthesis tool written by Stephen Williams.
vIDE is a fully featured, cross-platform, integrated environment for designing, testing and debugging Verilog applications.
VGI is a collection of tools which enables a designer to extract VHDL from blockdiagrams and state machines. Truthtable support is also included. The diagrams can be entered with tgif and then VGI tools can extract these diagrams. They can al so convert VHDL entity headers into tgif blocks which can then be used to assemble block diagrams.
Gnucap is a general purpose circuit simulator. It performs nonlinear dc and transient analyses, fourier analysis, and ac analysis. It is fully interactive and command driven.
gdspsim is a TMS320C54x dsp simulator with a gtk+ front end.
TMS320Cx DSP GNU Tools are ports of gcc, binutils, gdb for the C3x and C4x DSPs by Michael Hayes. The gdb port has a builtin simulator with many nifty features.