[SI-LIST] Re: Do you really ship products at BER 10e-xx ?
- From: "Henson, Bradley S" <Bradley.S.Henson@xxxxxxxxxx>
- To: <Chris.Cheng@xxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Wed, 13 Apr 2005 07:14:41 -0700
Well, I actually work in an area that designs space processors, so I am
truly involved with cosmic ray (heavy ion) SEUs and these Gbaud links. I
doubt "cosmic rays" are causing many ground-based equipment errors of
any consequence. Some Seu effects can be observed in aircraft, due
mainly to neutrons. Solar flare protons can cause upsets. It turns out
that the atmosphere attenuates most of these effects to a pretty low
level. I have read that some companies do system SEU reliability testing
in Denver...I don't recall the details.
In the application I was describing in my first post, the root problem
turned out to be a combination of non-ideal analog power filtering at
the receiver ASIC and what appeared to be a receiver that did not
operate reliably with an input that was better than required (i.e., the
channel, transmitter etc. were all well within requirements). I never
got to finish characterizing the receiver to determine why it did not
meet spec.
-----Original Message-----
From: Chris Cheng [mailto:Chris.Cheng@xxxxxxxxxxxx]=20
Sent: Tuesday, April 12, 2005 2:47 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Do you really ship products at BER 10e-xx ?
I have heard similar case from a third party and the customer service
engineer starts to explain, "of course, its cosmic rays" with a straight
face. I can't say how many people remains sitting on their chairs and
not flipping over after that. But it is not my personal experience so
that's why I am curious. Thanks for sharing though.
-----Original Message-----
From: Henson, Bradley S [mailto:Bradley.S.Henson@xxxxxxxxxx]
Sent: Tuesday, April 12, 2005 2:35 PM
To: Chris.Cheng@xxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] Do you really ship products at BER 10e-xx ?
This could make an interesting topic. I have to say that in general, I
have noticed the same trend: Links work so well the BER is hard to
determine (lots of test time or link-stress)-or- the links are totally
messed up. However, I did get called in to troubleshoot a Fibre channel
application that was just marginal on some of the links. By that I mean
they would almost make the spec 1E-12 BER sometimes, but usually fell
short. Some days they operated considerably poorer than 1E-12, but not
pure garbage.=20
-----Original Message-----
From: Chris Cheng [mailto:Chris.Cheng@xxxxxxxxxxxx]=20
Sent: Tuesday, April 12, 2005 1:49 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Do you really ship products at BER 10e-xx ?
I've been shipping Gb/s serial products for a while and have my share of
fail parts. However, I have yet to see a physical channel that is not
either working like a charm or just fall on its face and barfing errors
like crazy. Sure, chips or disk can fail and generates errors but no
flaky channels that spits an error every other hour or days. To me, the
channel is either have a BER that is near 1 (barfing errors like crazy)
or near 0 (never fail, or at least approaching the life of the product
it is attached to).=20
Are we just kidding ourselves with these fancy BER analyzers or jitter
instruments ? Do you really let a machine runs at say BER 10e-12 and say
"ah ha, it only fails once a day and let's ship it" ? Is BER really
meant for IEEE spec committees and not for real engineers who actually
have to ship a product ?
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