[SI-LIST] Re: Simulate 100MHz DRAMs for long term failures?!?!
- From: "Dimiter Popoff" <dp@xxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>, <dburns@xxxxxxxxxx>
- Date: Wed, 17 Aug 2005 23:16:01 +0300
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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