Javier Castillo <jcastillo@opensocdesign.com> wrote in message news:<Xns95647797DF637jcastilloopensocdesi@193.147.184.15>...

Hi Javier,
please see by comments below.
 
>   I dont want to have a discussion about what is better, because is obvious 
> that actually Verilog or VHDL are more mature HDLs and SystemC is a newbie. 
> The thing I want to transmit is that systemC can be used for RT design with 
> its current limitations. I say current because the SystemC Synthesis 
> Working Group is working in improve the SystemC capabilities in order to 
> make SystemC a RT solution as Verilog is.

I am convinced that it is possible to develop RTL using SystemC. More
than that, I am also convinced that, with some efforts, it will be
possible to develop RTL using Perl or any other language. The question
will be: how easy will be to sell it to designers.
Working Group effors are not sufficient to make SystemC a RTL Solution
as Verilog is. It is about the whole chip design infrastructure. It
took decades of common effort to bring Verilog-based design
infrastructure to the current level.  Then, the trend as I see is to
reduce, but not increase the number of RTL languages. SystemVerilog is
targeting this goal, inheriting most of useful RTL constructs from
VHDL. In fact, there is no value to express the same design intent in
different languages. As long as single language allows designers to
express all he/she needs, there is no need for another one.

> About your comments, I am agree in some of them because is obvious that 
> tools have a Verilog input and doesnt support SystemC. This Verilog input 
> is the reason to make a translation of the SystemC code, but I expect the 
> EDA suppliers will add SystemC support in their products. 

EDA suppliers will add SystemC support only if there will be business
case for it. Business case will be developed if designers will be
willing to pay money for the ability to develop RTL with SystemC. It
may not happen in the nearest feature.


> But I am not agree in other things, for example when you said:
> 
> > In addition to design, I also doubt that SystemC is a good choise for
> > the whole verification environment. For the system-level verification,
> > it is a good choise since it allows seamless interoperability with the
> > software. For the functional verification, verification-specific
> > languages (HVL)or SystemVerilog would be much better choise.
> > Functional verification requires advanced coverage, random generation,
> > assertion support as well as may other items such as random stability
> > etc. I doubt that SystemC has similar capabilities comparing to HVLs
> > or SV.
> 
> One of the strongest features of SystemC is the verification capabilities. 
> The SystemC Verification Library provides random generation, transaction 
> recording and many other features. Assertion or advance coverage is not 
> possible, the only thing you can do is a line coverage metric using GNU 
> gcov program. But as I said I expect EDA vendors will supply a SystemC 
> front end in their products. 

SystemC has good enough support for transaction-based, system-level
verification. It does not have almost any support for cycle-precised
verification, such as sequences, properties, assertions, coverage
constructs etc. This is natural, since SystemC, according to it's
name, targets system-level modeling and verification.


Regards,
Alexander Gnusin

Hello:

  I dont want to have a discussion about what is better, because is obvious 
that actually Verilog or VHDL are more mature HDLs and SystemC is a newbie. 
The thing I want to transmit is that systemC can be used for RT design with 
its current limitations. I say current because the SystemC Synthesis 
Working Group is working in improve the SystemC capabilities in order to 
make SystemC a RT solution as Verilog is.

About your comments, I am agree in some of them because is obvious that 
tools have a Verilog input and doesnt support SystemC. This Verilog input 
is the reason to make a translation of the SystemC code, but I expect the 
EDA suppliers will add SystemC support in their products. 

But I am not agree in other things, for example when you said:

> In addition to design, I also doubt that SystemC is a good choise for
> the whole verification environment. For the system-level verification,
> it is a good choise since it allows seamless interoperability with the
> software. For the functional verification, verification-specific
> languages (HVL)or SystemVerilog would be much better choise.
> Functional verification requires advanced coverage, random generation,
> assertion support as well as may other items such as random stability
> etc. I doubt that SystemC has similar capabilities comparing to HVLs
> or SV.

One of the strongest features of SystemC is the verification capabilities. 
The SystemC Verification Library provides random generation, transaction 
recording and many other features. Assertion or advance coverage is not 
possible, the only thing you can do is a line coverage metric using GNU 
gcov program. But as I said I expect EDA vendors will supply a SystemC 
front end in their products. 


> 1. Translation problems. I am really suspicious about "complete
> automatization" of language translation process. The problem is to
> make it work in ALL the cases. The easiest way to cleanup translation
> may be to reduce "translatable" subset in SystemC. It may not be a
> problem, but then it reduces "synthesizable" subset of SystemC and
> converts it to even more limited subset of synthesizable Verilog RTL.
> 2. Descriptive power.
> Verilog as a language was developed for RTL coding and constantly
> improves during years of practice. For example, Verilog 2001 and then
> SystemVerilog defines new useful constructs such as always_comb,
> always_ff etc allowing designer to specify design intent in a way that
> tools can verify. I doubt that SystemC has similar operator or can
> produce them during code translation.

We are talking about using SystemC as a RT language, and as a RT language 
you can do the same things you make in Verilog. Verilog and SystemC are 
different, and since they are different some things are described in a 
different way, for example assign statement in Verilog has to be translated 
into a combinational process in SystemC, but it can be translated. I think 
that all the Verilog RT subset has translation into SystemC.


Regards

Javier Castillo
jcastillo@opensocdesign.com
www.opensocdesign.com

glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote in message news:<ci52f3$14o$1@gnus01.u.washington.edu>...
>                                             In hardware, everything
> at least has the possibility of being active all the time, and the
> language should emphasize that.

Nope.  A language should emphasize writing demonstrably correct programs.

> Consider the ability to port a serial algorithm written in C to a
> hardware implementation of that algorithm.

Yes, consider that.  Assuming that you're using multiple cycles, you're
reusing clocked storage, pipelining, or both.  Between said storage,
you've got acyclic or converging logic, and the correctness of the
latter, not to mention its timing, is very hard to verify.

Note that expressing clocked storage correctly in Verilog is not
straightforward.  (Disagree?  Explain why folks have problems with
storage they didn't intend or don't get storage they do intend.)
It's hard to do worse with C, and easy to do better.  (No, the
resulting C doesn't look much like sequential C, but so what?)

With the exception of don't cares, acyclic logic between storage elements
is just as easy to express in C as any HDL.  The only possible advantage
for HDLs is converging cyclic logic without control signals.

I don't think that HDLs are going to make up ground with better ways to
designate clock signals.

-andy

Alexander Gnusin wrote:

> I do believe, that it is possible to write design in SystemC. There
> may be some advantages of this approach for people with strong C
> background. There are obviously drawbacks too, and I would like to
> outline some of them.

Personally, I am against HDL's that are more C like than verilog.

To me, they make people believe that one can think serially, as
when writing in a programming language.  In hardware, everything
at least has the possibility of being active all the time, and the
language should emphasize that.

Consider the ability to port a serial algorithm written in C to a
hardware implementation of that algorithm.

-- glen

On Wed, 08 Sep 2004 19:51:24 GMT, Jos De Laender <DoesntMatter@Somewhere.org> wrote:
>A good starting point , in my opinion , to gain some insight in the 
>matter is asking :
>why would _you_ think SystemC is faster or slower ?
>Jos

and

On Wed, 8 Sep 2004 13:26:32 -0700, "Russell Fredrickson" <russell_fredrickson@hp.com> wrote:
> ....
>One of the points of SystemC is to enable you to model
>and simulate things at a HIGHER level of abstraction than RTL.  If you write
>code at the RT level -- it will probably always simulate on the same order
>of magnitude whether it's Verilog or SystemC -- in fact since the Verilog
>simulators are more mature -- Verilog may simulate faster than SystemC
>(though I haven't done the exact measurements myself and it is simulator
>dependent).

I believe pretty much everything I read. Here is a quote from
a recent article by Shawn McCloud, High-Level Synthesis Product
Manager, Mentor Graphics Corporation.

     http://www.xilinx.com/publications/xcellonline/xcell_50/xc_mentor-esl50.htm

This is about half way through the article, in the print version on page
49 is the following:

"One advantage of SystemC is that it simulates as much as 100 times faster
 than an equivalent RTL representation specified at the same level of
 abstraction. However, to make a SystemC representation suitable for RTL
 generation or direct C synthesis, designers would need to write it at
 nearly the same level of abstraction as hand-translated RTL, which largely
 negates the advantages of using it in the first place."

That doesn't mean that the above is true, but here we see Mentor promoting
it that way.

Philip Freidin

For the US news media, there is nothing so important
or relevant, that it can't be ignored in favor of
some new, bright and shiny irrelavancy.

Javier Castillo <jcastillo@opensocdesign.com> wrote in message news:<Xns955F6B1A9D131jcastilloopensocdesi@193.147.184.15>...
> Hello:
>If you dont believe me ...

I do believe, that it is possible to write design in SystemC. There
may be some advantages of this approach for people with strong C
background. There are obviously drawbacks too, and I would like to
outline some of them.

1. Translation problems. I am really suspicious about "complete
automatization" of language translation process. The problem is to
make it work in ALL the cases. The easiest way to cleanup translation
may be to reduce "translatable" subset in SystemC. It may not be a
problem, but then it reduces "synthesizable" subset of SystemC and
converts it to even more limited subset of synthesizable Verilog RTL.

2. Descriptive power.
Verilog as a language was developed for RTL coding and constantly
improves during years of practice. For example, Verilog 2001 and then
SystemVerilog defines new useful constructs such as always_comb,
always_ff etc allowing designer to specify design intent in a way that
tools can verify. I doubt that SystemC has similar operator or can
produce them during code translation.

3. Need to maintain 2 code versions. Despite of Javier's opinion that
it is not a problem, I do see the need to maintain separately Verilog
version of RTL code. First, synthesis, STA and Equivalence checking
tools require verilog as an input. Then, there is a need to use
library cells, memories, DFT logic such as MBIST and JTAG, PLLs etc
etc. Do we have all this design infrastructure developed for SystemC?

4. Synthesis-STA-driven design modifications. These are very popular,
their intent is to improve timing performance of design. Translation
will complicate this process as well.

5. Maintenance effort. Designers cannot escape working and knowing
Verilog RTL. So they'll end up working with 2 languages as well as
constantly maintain functional equivalence between SystemC and Verilog
design representations.

In addition to design, I also doubt that SystemC is a good choise for
the whole verification environment. For the system-level verification,
it is a good choise since it allows seamless interoperability with the
software. For the functional verification, verification-specific
languages (HVL)or SystemVerilog would be much better choise.
Functional verification requires advanced coverage, random generation,
assertion support as well as may other items such as random stability
etc. I doubt that SystemC has similar capabilities comparing to HVLs
or SV.

Finally, there are already tools fo more efficient C-to-Verilog
integration than PLI provides. For example, VCS has DirectC interface.
Similar interface is also defined in SystemVerilog standard.

Regards,
Alexander Gnusin

The one we are using is the Cadence Insicive Unified Simulator.  I know
Mentor has a version as well (don't know about Synopsys).  I don't know
about the Mentor version -- but The Cadence implementation is very nice in
that you can do things like call Verilog functions/tasks from SystemC (and
in the next version -- IUS 5.4 -- you are supposed to be able to call
SystemC functions from Verilog), instantiate SystemC inside Verilog (and
vice versa), directly access Verilog memories from SystemC, etc.  In
addition, they do have an integrated environment debug environment and a
good transaction recording facility (from what I can tell -- I haven't used
the transaction recording too much yet).  Cadence also has it's hands in
donating major portions of the SystemC add on libraries (SCV, TLM
methodology) -- so they really good in terms of full support for most
anything you want to do with SystemC.  Again, I really don't have any data
on Mentor's version, so I can't comment on it.

    Russell


"Varun Jindal" <varunjindal@yahoo.com> wrote in message
news:a132b4b3.0409092047.6e2980bc@posting.google.com...
> Hello Russell,
>
> I have a model in SystemC and to simulate it with Verilog testbench, i
> am using a PLI (for VCS). you have mentioned SystemC/Verilog
> co-simulators, but i have not been able to find any. Does anybody know
> any such simulators available?
>
> Thanks in Advance.
>
> regards
> Varun.
>
>
>
>
>
> "Russell Fredrickson" <russell_fredrickson@hp.com> wrote in message
news:<chnpum$vq2$1@news.vcd.hp.com>...
> > Okay -- I think you (and others who replied) have missed one of the main
> > points of SystemC.  One of the points of SystemC is to enable you to
model
> > and simulate things at a HIGHER level of abstraction than RTL.  If you
write
> > code at the RT level -- it will probably always simulate on the same
order
> > of magnitude whether it's Verilog or SystemC -- in fact since the
Verilog
> > simulators are more mature -- Verilog may simulate faster than SystemC
> > (though I haven't done the exact measurements myself and it is simulator
> > dependent).  The talk about SystemC being faster is making the
assumption
> > that you write SystemC at a higher level of abstraction than your RTL.
> > Though, as a side note, there are several vendors out there who will
> > translate Verilog to optimized C/C++ or SystemC and then get about a 10x
or
> > more improvement over Verilog (TenisonEDA and Carbon Systems come to
mind).
> >
> > In my opinion -- writing RTL in SystemC is a waste of time since Verilog
(or
> > VHDL) is more suitable to that task (and maintaining RTL descriptions in
TWO
> > languages seems like even more of a waste of time and is asking for
> > trouble).  In any case you can always have Verilog and SystemC co-exist
by
> > interfacing SystemC to RTL through a PLI or using one of the unified
> > SystemC/Verilog simulators.
> >
> > My point -- adopting a new language without also adopting a new
methodology
> > that makes use of the power of the language will only give you limited
> > benefit (if any benefit at all).  For example, when going from schematic
> > capture to Verilog -- many people at first used Verilog just like a
textual
> > schematic capture tool.  This got them using an HDL (which is a step in
the
> > write direction), but they really didn't get the full advantage of the
HDL
> > until they started writing RTL that then could then synthesized into
gates
> > (basically raising the level of abstraction at which they modeled their
> > design).
> >
> > So for SystemC some of the power of the language comes in being able to
do a
> > top-down implementation where you start with a high-level architectural
> > model and refine it down to the RTL level (or perhaps use a behavioral
> > synthesis tool once you get down to a appropriate level of abstraction).
> > Also the SystemC Verification extensions (SCV) is another way SystemC
can be
> > used to improve your verification effort (here again -- you will
probably
> > need to use a different verification methodology to make full use of
SCVs
> > capabilities).  I'll stop there -- if you look hard enough you should be
> > able to find other references talking about the new methodologies
enabled by
> > SystemC.
> >
> > I hope that helps,
> > Russell
> >
> >
> >
> > <singh.shailendra@gmail.com> wrote in message
> > news:ab4d6621.0409072214.6b8ae5a@posting.google.com...
> > > Hi,
> > > Can anybody elaborate on the speed of the simulation in systemC in
> > > comparision with Verilog. In our case we have used the systemC for
> > > the modeling of RTL design,  then verified the systemC RTL models. As
> > > a final step
> > > systemC RTL is converted into verilog RTL(line by line translation).
> > > we are surprised to see the both systemC models and Verilog models are
> > > running at almost same speed. Can you through some light on it, what
> > > went wrong in the process?
> > > is it systemC coding is not proper or may be testbench not written
> > > properly or
> > > if we code systemC and Verilog at same level of abstraction we should
> > > same speed only.

"Varun Jindal" <varunjindal@yahoo.com> wrote in message 
news:a132b4b3.0409092047.6e2980bc@posting.google.com...
> Hello Russell,
>
> I have a model in SystemC and to simulate it with Verilog testbench, i
> am using a PLI (for VCS). you have mentioned SystemC/Verilog
> co-simulators, but i have not been able to find any. Does anybody know
> any such simulators available?
    Modelsim, for one:  VHDL, verilog, and SystemC (to a limited extent.) 
Of course, you need the appropriate licen$e$.

>
> Thanks in Advance.
>
> regards
> Varun.

Jason

Hello Russell,

I have a model in SystemC and to simulate it with Verilog testbench, i
am using a PLI (for VCS). you have mentioned SystemC/Verilog
co-simulators, but i have not been able to find any. Does anybody know
any such simulators available?

Thanks in Advance.

regards
Varun.





"Russell Fredrickson" <russell_fredrickson@hp.com> wrote in message news:<chnpum$vq2$1@news.vcd.hp.com>...
> Okay -- I think you (and others who replied) have missed one of the main
> points of SystemC.  One of the points of SystemC is to enable you to model
> and simulate things at a HIGHER level of abstraction than RTL.  If you write
> code at the RT level -- it will probably always simulate on the same order
> of magnitude whether it's Verilog or SystemC -- in fact since the Verilog
> simulators are more mature -- Verilog may simulate faster than SystemC
> (though I haven't done the exact measurements myself and it is simulator
> dependent).  The talk about SystemC being faster is making the assumption
> that you write SystemC at a higher level of abstraction than your RTL.
> Though, as a side note, there are several vendors out there who will
> translate Verilog to optimized C/C++ or SystemC and then get about a 10x or
> more improvement over Verilog (TenisonEDA and Carbon Systems come to mind).
> 
> In my opinion -- writing RTL in SystemC is a waste of time since Verilog (or
> VHDL) is more suitable to that task (and maintaining RTL descriptions in TWO
> languages seems like even more of a waste of time and is asking for
> trouble).  In any case you can always have Verilog and SystemC co-exist by
> interfacing SystemC to RTL through a PLI or using one of the unified
> SystemC/Verilog simulators.
> 
> My point -- adopting a new language without also adopting a new methodology
> that makes use of the power of the language will only give you limited
> benefit (if any benefit at all).  For example, when going from schematic
> capture to Verilog -- many people at first used Verilog just like a textual
> schematic capture tool.  This got them using an HDL (which is a step in the
> write direction), but they really didn't get the full advantage of the HDL
> until they started writing RTL that then could then synthesized into gates
> (basically raising the level of abstraction at which they modeled their
> design).
> 
> So for SystemC some of the power of the language comes in being able to do a
> top-down implementation where you start with a high-level architectural
> model and refine it down to the RTL level (or perhaps use a behavioral
> synthesis tool once you get down to a appropriate level of abstraction).
> Also the SystemC Verification extensions (SCV) is another way SystemC can be
> used to improve your verification effort (here again -- you will probably
> need to use a different verification methodology to make full use of SCVs
> capabilities).  I'll stop there -- if you look hard enough you should be
> able to find other references talking about the new methodologies enabled by
> SystemC.
> 
> I hope that helps,
> Russell
> 
> 
> 
> <singh.shailendra@gmail.com> wrote in message
> news:ab4d6621.0409072214.6b8ae5a@posting.google.com...
> > Hi,
> > Can anybody elaborate on the speed of the simulation in systemC in
> > comparision with Verilog. In our case we have used the systemC for
> > the modeling of RTL design,  then verified the systemC RTL models. As
> > a final step
> > systemC RTL is converted into verilog RTL(line by line translation).
> > we are surprised to see the both systemC models and Verilog models are
> > running at almost same speed. Can you through some light on it, what
> > went wrong in the process?
> > is it systemC coding is not proper or may be testbench not written
> > properly or
> > if we code systemC and Verilog at same level of abstraction we should
> > same speed only.