Re: [vhdl-200x], vital issues

Subject: Re: [vhdl-200x], vital issues
From: Jim Lewis (
Date: Thu Mar 06 2003 - 19:54:09 PST

I think I sent that too quick. What I want is speed
that is at least the same as Verilog.
What I was thinking of when I said netlist was library.
I am ok with having a VHDL netlist of gate library elements.
What I want is the library elements in the VHDL netlist be
able to use Verilog library components and primitives.

Again one library format common to both languages would
have great benefits for all.


Jim Lewis wrote:
> If we were to develop a new library solution, someone
> would have to spend money to develop sign-off quality
> vendor libraries. In the current economy, do they have
> money to support two different netlist formats for
> sign-off quality libraries?
> The current VHDL gate level libraries are slow.
> According to a presentation at DVCon, Verilog
> gate-level libraries are 4X faster than VHDL libraries.
> If we can read and execute Verilog gate-level libraries, I
> get the speed I want, without having to pay for two licenses
> to run one simulation. Vendors (EDA and silicon) get the
> advantage of only having to support one library format.
> I suppose if you could give me a library format that would
> simulate faster than Verilog gates, I might be interested.
> Cheers,
> Jim
>> Actually the VHDL netlist is not as much as a problem as the
>> VHDL gate models. It would be nice to have precompiled libraries,
>> whether they came from Verilog or whatever is not of "vital"
>> importance. I'd be glad to see less of vital models, they do
>> not show VHDL in a good light.
>> The netlist itself does not lead to inefficiencies, it contains
>> no models, just connectivity. I don't see savings to be gained
>> by reading in a Verilog netlist over a VHDL netlist.
>> There are still of course problems reading netlists, mostly
>> environmental, library related since the netlist is multi-use.
>> Not clear things are better in Verilog.
>> The SDF is the same regardless, excepting of course that VHDL
>> "out" ports cannot be read so one has to artificially inflate
>> the design before the VHDL and Verilog netlist signals can have the
>> same names. (this issue is on our list) This would be a real
>> headache if you tried to read a Verilog netlist into VHDL.
>> It is worth noting the trend is away from having setup-hold, skew,
>> etc. checked in the models. These things are checked in the STA,
>> where there is more information than the SDF has. For simulation,
>> there is more interest in fast models. So we could have simpler
>> VHDL gate models for simulation, if there was any incentive for
>> the simulation people to supply them (did you ever see software
>> get smaller?)
>> --Rob
>> Jim Lewis wrote:
>>> Francoise,
>>> I see there being two aspects to this.
>>> 1) Read Verilog Gate-level Netlists
>>> Vital is not enjoying the wide support we wished for.
>>> Vital is also slow compared to Verilog gate-level netlists.
>>> If Vital died, silicon vendors would only need to support
>>> one gate-level library format. EDA vendors would no longer
>>> need to support Vital. Hence, this would be good for both.
>>> However, the current situation is not good for VHDL designers,
>>> because to use a VHDL testbench with a Verilog gate-level
>>> netlist will cost me two licenses, one for VHDL and one
>>> for Verilog. Note for a Verilog designer it would only
>>> cost one license.
>>> To benefit both users and vendors, it would be best if
>>> Verilog gate-level netlists were included as part of the
>>> langauge.
>>> 2) Standardized Verilog Interface
>>> Standardize how to connect a Verilog design to VHDL.
>>> This would take us away from a Vendor specific
>>> implementation (which at the current time may or may not
>>> be identical, but it would be nice if it were documented
>>> somewhere in the standard).
>>> This of course should and will likely cost two licenses.
>>> Cheers,
>>> Jim
>>> Francoise Martinolle wrote:
>>>> I noticed in the priority spreadsheet that a few people (Jim Lewis,
>>>> Williams and Bishop)
>>>> have voted for read and simulate Verilog netlists.
>>>> I was wondering of one of them could provide a short description of
>>>> this request.
>>>> thanks
>>>> Francoise

Jim Lewis
Director of Training   
SynthWorks Design Inc. 

Expert VHDL Training for Hardware Design and Verification ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This archive was generated by hypermail 2b28 : Thu Mar 06 2003 - 20:06:28 PST