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0 pointsJoachimS1mo ago0 comments

The question for me is, where do I catch, describe the physical reality the model describes? A simulation model can be very elegant. But does it represent how physical things really behave? Can we even expect to do that at RTL, or further down the design flow? As the name suggest, we are talking about transferring data between registers. In the RTL that is what I can expect to describe.

At the end of the day, what I write will become an electrical circuit - in a FPGA or an ASIC (or both), having the complex exact modelling with wire delays, capacitance, cross talk, cell behavior too early makes it impossibly to simulate fast enough to iterate. So then we need to have a more idealized world, but keeping in mind that (1) it is an idealized world and (2) sooner or later the model will be the rubber on the road.

To me, Verilog and SystemVerilog allow me to do this efficiently. Warts and all.

Oh, and also, where in my toolchain is my VHDL model translated/transformed into Verilog? How good is that translation? How much does the dual licensing cost.

Things like mixed language simulation, formal verification between a verilog netlist and RTL in Verilog, mapping to cell libraries in Verilog. Integration of IP cores written in SystemVerilog with your model?

Are the tools for VHDL as well tested as with code in Verilog? How big is the VHDL team at the tool vendor, library vendor, IP vendor, fab vendor compared to the Verilog, SV team? Can I expect the same support as a VHDL user as for Verilog? How much money does a vendor earn from VHDL customers compared to Verilog, SV? How easy is it to find employees with VHDL experience?

VHDL may be a very nice language for simulation. But the engineering, business side is messy. And dev time, money can't be ignored. Getting things as fast and cheap as possibly still meeting a lot of functional, business requirements is what we as engineers are responsible for. Does VHDL make that easier or not?

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tverbeure1mo ago

> where in my toolchain is my VHDL model translated/transformed into Verilog?

It's not? Why would it?

As much as I like Verilog, VHDL is a first class RTL language just like Verilog. I've done plenty of chips that contain both VHDL and Verilog. They both translate directly to gate level.

These days, most EDA tools use Verific parser and elaborator front-ends. The specific tool magic happens after that and that API is language agnostic.

> How easy is it to find employees with VHDL experience?

On the East Coast and in Europe: much easier than finding employees with Verilog experience. (At least that was the case 20 years ago, I have no clue how it is today.)

One thing that has changed a lot is that SystemVerilog is now the general language of choice for verification, which helps give (System)Verilog an edge for RTL design too.

JoachimSOP1mo ago

Involved in FPGA and ASIC projects since 1997. Predominantly in Europe, nowadays more Asia and some in the US. Since ~2010 I have only seen VHDL in small chops targeting only FPGAs, and in government-heavy projects like defence and space. Nowadays these are also by and large SV. The ratio is something like one in VHDL for 20 Verilog, SV projects. They teach VHDL at universities, and then ppl get to experience SV as soon as they enter the market.

Typical issues are still as given before. Many small IP vendors, esp for communication, networking are using and understand, support only SV. I agree on SV for verification is a big driver.

novachen1mo ago

the geographic constraint is probably the real answer to "which is better" for most people. you learn what your team uses, what your local jobs demand. theoretical elegance matters less than "can i get hired next month"

Joel_Mckay1mo ago

Over the years I have run Altera, Lattice, and Xilinx... and almost all reasonably complex projects were always done in Verilog. If I recall Xilinx fully integrated its Synopsys export workflow a few years back, but not sure where that went after the mergers.

The Amaranth HDL python project does look fun =3

https://github.com/amaranth-lang/amaranth

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