[SI-LIST] Re: Fibre channel interconnect margins
- From: steve weir <weirsi@xxxxxxxxxx>
- To: Hal Murray <hmurray@xxxxxxxxxxxxxxx>
- Date: Tue, 04 Jul 2006 18:00:42 -0700
Hal, Gaussian noise is thermal. The thermal noise amplitude isn't
what tends to bite in links unless they are very long like undersea
optical links. In back planes and boards the noise will usually get
us as jitter.
I don't have numbers that would be useful to you for CPUs. You might
be able to find the energy numbers for the required amplitudes by
searching on SEUs which are becoming a perceivable problem. Then we
could work that back to the bulk resistance of the material and
probably come up with a reasonable number for thermal noise, and an error rate.
Regards,
Steve.
At 05:41 PM 7/4/2006, Hal Murray wrote:
> > Hal, the Gaussian model really does apply and eventually your CPU
> > does make mistakes. It tends to happen at such a low rate we all
> > blame it on the software or input devices that make mistakes millions
> > of times more frequently. When it comes to CPUs I am not even sure
> > where to begin sifting transistor switching errors from other sources
> > because the event frequency is so low.
>
>I believe it will happen if I wait long enough, but I don't have a good feel
>for the numbers.
>
>I expect that I would have to wait something like the age-of-universe rather
>than just a short time like several/many years which is the time scale for
>most error mechanisms. (at least in a well designed system)
>
>
>What's the SNR for a normal CMOS signal? (either on chip or between chips)
>
>I'm only interested in the Gaussian part of the noise.
>
>Where does real-life Gaussian noise come from? Thermal/Johnson? If so, is
>the R the output resistance of the driving transistor? What's a typical
>number?
>
>
>What's the (Gaussian) SNR on a Fibre Channel link? (copper and fiber)
>
>
>
>--
>The suespammers.org mail server is located in California. So are all my
>other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
>commercial e-mail to my suespammers.org address or any of my other addresses.
>These are my opinions, not necessarily my employer's. I hate spam.
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
