Comparison of VHDL to Other Hardware Description Languages

VHDL Disadvantages

• VHDL is verbose, complicated and confusing
• Many different ways of saying the same thing
• Constructs that have similar purpose have very different syntax (case vs. select)
• Constructs that have similar syntax have very different semantics (variables vs signals)
• Hardware that is synthesized is not always obvious (when is a signal a flip-flop vs latch vs combinational)

VHDL Advantages

• VHDL supports unsynthesizable constructs that are useful in writing high-level models, testbenches and other non-hardware or non-synthesizable artifacts that we need in hardware design.
• VHDL can be used throughout a large portion of the design process in different capacities, from specification to implementation to verification.
• VHDL has static typechecking—many errors can be caught before synthesis and/or simulation.
• VHDL has a rich collection of datatypes
• VHDL is a full-featured language with a good module system (libraries and packages).
• VHDL has a well-defined standard.
  

VHDL and Other Languages

• VHDL vs Verilog
• Verilog is a "simpler" language: smaller language, simple circuits are easier to write
• VHDL has more features than Verilog
• richer set of data types and strong type checking
• VHDL offers more flexibility and expressivity for constructing large systems.
• The VHDL Standard is more standard than the Verilog Standard
• VHDL and Verilog have simulation-based semantics
• Simulation vendors generally conform to VHDL standard
• Some Verilog constructs don't simulate the same in different tools
• VHDL is used more than Verilog in Europe and Japan
• Verilog is used more than VHDL in North America
• South-East Asia, India, South America - More Democratic
• VHDL vs SystemC
• System C looks like C —familiar syntax
• C is often used in algorithmic descriptions of circuits, so why not try to use it for synthesizable code as well?
• If you think VHDL is hard to synthesize, try C....
• SystemC simulation is slower than advertised
• VHDL vs Other Hardware Description Languages
• Superlog: A proposed language that was based on Verilog and C. Basic core comes from Verilog. C-like extensions included to make language more expressive and powerful. Developed by the Co-Design company, but no longer under active development. Superlog has been superseded by SystemVerilog, see below.
• SystemVerilog: A language originally proposed by Co-Design and now standardized by Accellera, an organization aimed at standardizing EDA languages. SystemVerilog is inspired by Verilog, Superlog, and System-C. SystemVerilog is a superset of Verilog aimed to support both high-level design and verification.
• Esterelle: A language evolving from academia to commercial viability. Very clean semantics. Aimed at state machines, limited support for datapath operations.