Re: gEDA-dev: Last call for input on SOW for Linux Fund....

[Dan McMahill <dan-at-NOSPAMmcmahill_dot_net>]

John Doty wrote:
> On Dec 3, 2008, at 7:40 AM, Svenn Are Bjerkem wrote:
> 
>> Ken Kundert knows what he is talking about
> 
> I don't think so. He thinks mixed-signal design is like computer  
> programming. But it's not: to do it well you have to start from the  
> *physics* of what you're trying to accomplish.

I guess thats why a huge number of complex commercial chips are verified 
using the simulator that Ken designed?  He certainly has his view point 
about things that you may disagree with, but to say he doesn't know what 
he is talking about is pretty far off base.

> I wonder what tools Paul Horowitz uses these days. *There's* a guy  
> who understands mixed signal disign and can write clearly about it.

I wonder if Paul Horowitz does complex chip designs.  The reality of it 
is that simulation tools have never been that useful or in my opinion 
critical for the sorts of circuits in his book.  But for the IC industry 
which is really where Verilog-{HDL,A,AMS} are used, simulation tools are 
critical and those 3 in particular fill a critical need.


>> and he offers enough
>> information on http://www.designers-guide.org/index.html for anybody
>> interested in AMS to get up to date on the advantages of doing things
>> the AMS way.
> 
> Kundert's book is what Al got me to buy. It's a sales pitch, not a  
> textbook: the signal to noise ratio is very low. Someone who has a  
> problem to solve doesn't want a bunch of hype on the advantages of a  
> tool: they want a roadmap that will allow them to find a solution.

12 pages of background and context
20 pages of sales pitch
 > 200 pages of reference material spelling out the language

doesn't sound like bad SNR to me.

When I can't quite remember the name of a function or the order of the 
arguments that is the book I reach for.  In contrast I have not reached 
for the Horowitz book since sophomore or junior in college 2 decades ago.

But... unless you have coughed up the money for the simulator its not so 
useful.  So my question for you is do you have access to Verilog-A or 
Verilog-AMS so that you have been able to try them out on a real design? 
    If you have used the tools, how did you learn about them?  If you 
haven't used the tools, I question how useful of a review you can give 
of a book that teaches the tools.


If you don't use tools like these, do your designs have large mixed 
signal components that are not easily broken apart?  By that I mean, do 
you have blocks that contain some subcells which are prohibitive for 
simulating at the transistor level but yet you have to have a model of 
them in place during a simulation because they are part of a feedback 
loop?  What tools do you use to handle that complexity?  How do you 
ensure that your million dollar mask set is going to produce silicon 
that is at least functional and doesn't have outright wiring errors or 
fundamental screw-ups in the block diagram?  How do you include the 
complex behavior of one block where 20 dB analog accuracy is sufficient 
in a simulation where 100 dB of analog accuracy is need for another 
block?  It's one thing to realize you need to buy a different op-amp for 
your board or add 15 blue wires.  It is another thing entirely when you 
find you just took a many month schedule hit and had to come up with 
another huge pile of cash for masks because you only did block level 
simulations on your chip.

Those are the sorts of real world problems which are solved every day 
using Verilog-{HDL,A,AMS}.  It is not hype or vaporware.

-Dan




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