[SI-LIST] Re: Simulate 100MHz DRAMs for long term failures?!?!
- From: "Douglas Burns" <dburns@xxxxxxxxxx>
- To: <dp@xxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Thu, 18 Aug 2005 08:51:02 -0400
Dimiter,
It's unfortunate that you do not want to talk about how you approached this
or other problems. I'd never call into question your design expertise and I
don't think that was the point of this entire chain. You have had multiple
sucessful projects, so you must be doing something right, but we all learn
something when we, as a group, discuss how we view problems and the approach
we take to solve them. That is where this list turns into an educational
classroom. Some of the best interchanges on this list occur when people
share some of the details of problems they are seeing and how they are
trying to solve a problem.
Just my 2 cents.
Best Regards
Doug
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On
Behalf Of Dimiter Popoff
Sent: Wednesday, August 17, 2005 4:16 PM
To: si-list@xxxxxxxxxxxxx; dburns@xxxxxxxxxx
Subject: [SI-LIST] Re: Simulate 100MHz DRAMs for long term failures?!?!
Doug,
your take on how a design process takes place is generally correct.
However, when I posted my first message I just supplied information
I had and I did not - nor do I now - want to tell my lifestory. I am not
interested
in explaining how I do my work and how very best I am, I let my work speak
for itself.
The number of complaint-free designs I have - owned by me or by other
people - during
the past 20 years suggests that there has been more than luck to it; I did
mention that. Now if anyone has problems to believe or swallow that,
well, too bad. Any further investigations on the matter will have
to go without my assistance, I have closed this design effort 5 years ago
and moved to other things.
Dimiter
------------------------------------------------------
Dimiter Popoff Transgalactic Instruments
http://www.tgi-sci.com
------------------------------------------------------
-------Original Message-------
> From: Douglas Burns <dburns@xxxxxxxxxx>
> Subject: [SI-LIST] Re: Simulate 100MHz DRAMs for long term failures?!?!
> Sent: Aug 17 '05 20:19
>
> Dimiter,
>
> I think what people are really stating is that a good design practice
> requires a design methodology
> to determine how to approach a design. In terms of the discussion, I
think
> the question being asked
> was what methodology did you use. It seems to me that you just didn't
guess,
> but used your
> experience from previous work to define your methodology. Scott gave a
good
> example of a
> methodology to determine the criticality of a signal for overshoot
concerns.
> If you used that type
> of methodology when doing your 5 year old design (i.e. your knew your
> risetime of your signal
> was much greater than the round trip delay of the signal or you reviewed
the
> spec's to see what
> the max overshoot spec was and determined by back of the envelope
> calculations that you had
> sufficient margin), then you used good engineering judgment when
assessing
> the risk of not
> simulating the design and the proper operation is due to your good
judgment.
> If however, you
> did not know the component overshoot spec or review the edgerate vs.
> interconnect length
> (pkg/etch/pkg) or other such review and you did just implemented it, then
> I'd agree that luck
> had a hand in the design. (That luck being we are talking about a 5 year
old
> technology and
> the edgerates were probably fairly slow compared today's edgerates and
the
> chip in question
> could probably support AC transients greater than 0.5V above DC, thus
fact
> that you see no
> failures would not be much of a surprise.)
>
> In terms of a consultants advice, a good consultant would not suggest
> simulating the obvious,
> but be able to identify where rules of thumb apply, where a design is on
the
> edge and simulation
> may be warranted, and lastly what parts of a design absolutely require
> analysis. That is the value of
> the consultant, to know the difference and how to solve issues that the
> customer may have little
> experience with. If they mislead the customer, the result is generally
the
> lack of repeat business
> and a bad reputation.
>
> Best Regards,
>
> Doug
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On
> Behalf Of Dimiter Popoff
> Sent: Tuesday, August 16, 2005 8:41 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Simulate 100MHz DRAMs for long term failures?!?!
>
>
> > But the conditions have to be "just right" to be able to do that....
>
> Being able to recognize these conditions is what makes one a design
> engineer.
>
> Dimiter
>
> (somewhat astonished at the interest a 5 year old design of mine can
> raise...
> seems there is no lack of people being keen on justifuying this or
> that overdesign decision they took)
>
> ------------------------------------------------------
> Dimiter Popoff Transgalactic Instruments
>
> http://www.tgi-sci.com
> ------------------------------------------------------
>
>
>
>
> -------Original Message-------
> > From: Aubrey_Sparkman@xxxxxxxx
> > Subject: [SI-LIST] Re: Simulate 100MHz DRAMs for long term failures?!?!
> > Sent: Aug 17 '05 03:07
> >
> > Jeff,
> > I absolutely LOVE your analogy. Heck, I'll even add to it. When I
was
> > younger, I actually put out a match in gasoline. But the conditions
> > have to be "just right" to be able to do that....=20
> >
> > Please DON'T try that at home!
> >
> > :-)
> >
> >
> > Aubrey Sparkman=20
> > Enterprise Engineering Signal Integrity Team
> > Dell, Inc.=20
> > Aubrey_Sparkman@xxxxxxxx=20
> > (512) 723-3592
> >
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
> > On Behalf Of Loyer, Jeff
> > Sent: Tuesday, August 16, 2005 6:59 PM
> > To: si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Simulate 100MHz DRAMs for long term failures?!?!
> >
> > I'll probably hate myself in the morning, but just can't help it...
> > (title of thread changed also)
> >
> > I was cleaning car parts yesterday. I had a flashback to cleaning
parts
> > in the 1970's when I was a mechanic. Cleaned 'em in gasoline, with a
> > cigarette hanging out of my mouth. Did it for years, never had a
> > problem. Worked with lots of people who had the same experience.
> >
> > My personal experience suggests that there's no danger in cleaning car
> > parts in gasoline while smoking cigarettes. Others suggest otherwise.
> > =3D20
> >
> > I might conclude that there's a conspiracy among folks to force me to
> > buy more expensive cleansers and quit enjoying a harmless vice while
> > engaged in brainless activities.
> >
> > Instead, I've long since decided that I was pretty lucky (though my
> > liver may later say otherwise). I use a very different method to
clean
> > parts now. Heck, I even quit smoking many years ago (it's a great
excuse
> > to spoil myself on my "quit smoking anniversary"!).
> >
> > While I think it's always good to question whether we're being
> > overcautious and expending resources on stuff we don't care about, I
> > think it's also prudent to worry about stuff that other very
> > knowledgeable people get upset about. =3D20
> >
> > I also know that often it isn't the super-duper fast busses that kill
a
> > platform - it's the "supposedly DC" or other slow bus that wasn't
given
> > a 2nd thought. It's risetime that kills us, not clock frequency.
=3D20
> >
> > And finally, one figure of merit for an engineer is whether they can
do
> > a quick "back-of-the-envelope" calculation that gives us an idea of
the
> > risk associated with a bus. I thought Scott did a nice job of that
> > (though I didn't look at it too intensely). Unless I could dispute
some
> > part of those calculations, I'd conclude the bus you're talking about
> > deserves consideration.
> >
> > My 2cents,
> > Jeff Loyer
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