Re: [f-cpu] the ghdl bomb

[nico <nicolas.boulay@ifrance.com>]

On Wed, 20 Nov 2002 11:39:32 CET
whygee@club-internet.fr wrote:

> heck ! the old simulation/emulation trouble
> pops up again .....
> 
> >De: nico
> >
> >> Hello,
> >> 
> >> Usually, "software people" don't like VHDL because "it is slow"
> >> and a C version of the source code has been started. This
> >> increases the size of the project because two versions of the
> >> sources must be written, maintained and checked against each others. The availability of a native GCC support reduces the
> >> need of a C version of the code and reduces the coding, testing
> >> and regression check efforts. This also provides a high
> >> speed simulation engine that doesn't require contributors
> >
> >high speed !!!!! It's a joke ?
> 
> "Everything is relative" (Einstein)

But not this sentence.

> and it's certainly going to be faster than
> vanilla or Simili. And you forgot the main
> point : it's free.
> 

Yep but not fast enought to develop program.

> >you will have a simulation time around 1:100000
> > and you want to debug program !
> At least if the program fails, we can know where the
> RTL model fails. And before giving numbers, one
> has to measure it....
> 

That's not really the point. Emulator are for developping software not debugging hardware.

Cedric wanted to develop a "model" to validate the architectural point. SystemC or other high level language are design to do so. Even C (mostly C in fact) to check algorythme.

> >That's not an emulator ! We could juste test few 10 ms (15 min) of test not much !
> >
> >Check leon, it vhdl exist but an emulator existe too !
> 
> The problem with an "emulator" is that it completely
> skips all the RTL level and dirty hacks are necessary
> to make it behave the same way. Sure it's "fast" (depending

No.

> on the complexity of the model and architecture) but a lot
> of efforts must be spent to keep the simulator and the
> emulator in synch. And this puts pressure on the development.

Sur, you have twice the work but emulator should be far simple.

> 
> Now, tell me who has ever written a F-CPU program that
> has a longer simulation time than a few seconds.

Have you ever run a few second rtl simulation run ? How long it will take to your opinion ?

> The longer program i know is the RC5 client from Cédric.
> 
> Finally, if you don't want to use GHDL, you're not forced.

fcpu will be written in VHDL to be synthetise. So GHDL could be used. But he only replace simili or freehdl or ...

nicO

> 
> >> YG
> YG
> 
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