[SI-LIST] Re: termination for routing 8 SDRAMs to single Processor
- From: steve weir <weirsi@xxxxxxxxxx>
- To: dp@xxxxxxxxxxx, <si-list@xxxxxxxxxxxxx>
- Date: Thu, 11 Aug 2005 00:23:08 -0700
Dimiter, as we just finished discussing, the I/Os on the 8420 may be
considerably more robust than on other parts. We also never established
what kind of overshoot you had.
The problems caused by overshoot on modern silicon are well documented.
Dr. Deming would not be happy with your conclusion that a single unit
sample predicts what a larger population will do. Before we can gainfully
use a sample, we need to know what our variations are. This is no slight
against you, it is just the tyranny of SPC.
Steve.
At 10:07 AM 8/11/2005 +0300, Dimiter Popoff wrote:
>So you have seen many prototypes which operated continuously
>for about 4 years and exhibit problems once they go into mass production.
>Well, kucky me. I had no problems.
>
>Dimiter
>
>------------------------------------------------------
>Dimiter Popoff Transgalactic Instruments
>
>http://www.tgi-sci.com
>------------------------------------------------------
>
>
>
>
>-------Original Message-------
> > From: Kenneth W. Egan <kegan@xxxxxxxxxxxxx>
> > Subject: RE: [SI-LIST] Re: termination for routing 8 SDRAMs to single
> Processor
> > Sent: Aug 11 '05 09:47
> >
> > ??
> > Depends upon the characterization of the silicon on both sides. So it's a
> > statistics thing. How many units have you shipped ? This is the
> determining
> > factor, not one unit for a period of time.
> >
> > Overshoot is an issue for many silicon vendors. For example, one of TI's
> > DSP's call out max of 4.3v overshoot for 3.3v I/O on their SDRAM I/F. But
> > the real piece is the spec that indicates, not only 4.3v, but also
> only over
> > a max of 30% of the clock period. So this may indicate junction
> > heating/oxide breakdown issues with the process node, or design of their
> > device.
> >
> > I've seen plenty of prototypes that work fine, put them in mass
> production,
> > and these issues start cropping up.
> >
> > KWE
> >
> > -----Original Message-----
> > From: Dimiter Popoff [mailto:dp@xxxxxxxxxxx]
> > Sent: Thursday, August 11, 2005 12:56 AM
> > To: Kenneth W. Egan; aavinda12@xxxxxxxxx; si-list@xxxxxxxxxxxxx
> > Subject: RE: [SI-LIST] Re: termination for routing 8 SDRAMs to single
> > Processor
> >
> > Is about 4 years practically continuous operation good enough?
> > The design has demonstrated it.
> >
> > Dimiter
> >
> > ------------------------------------------------------
> > Dimiter Popoff Transgalactic Instruments
> >
> > http://www.tgi-sci.com
> > ------------------------------------------------------
> >
> >
> >
> >
> > -------Original Message-------
> > > From: Kenneth W. Egan <kegan@xxxxxxxxxxxxx>
> > > Subject: RE: [SI-LIST] Re: termination for routing 8 SDRAMs to single
> > > Processor
> > > Sent: Aug 11 '05 05:21
> > >
> > > The question might not be one of stability, but one of reliability in
> > > the long term. Sure, you'll probably meet setup and hold to/from the
> > SDRAM.
> > > However, SDRAM typically has some pretty hot drivers (that I've seen,
> > > simulated and measured in circuit ) and the real issue is over
> > > stressing The input protection on the receiver, i.e. overshoot issues.
> > >
> > > Failure modes in this case may not occur until much later in time.
> > >
> > > KWE
> > >
> > >
> > > -----Original Message-----
> > > From: si-list-bounce@xxxxxxxxxxxxx
> > > [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Dimiter Popoff
> > > Sent: Wednesday, August 10, 2005 8:00 PM
> > > To: aavinda12@xxxxxxxxx; si-list@xxxxxxxxxxxxx
> > > Subject: [SI-LIST] Re: termination for routing 8 SDRAMs to single
> > > Processor
> > >
> > > I have rooted 8 x8 SDRAMs to an 8240 without any terminations and it
> > > worked remarkably stable. However, I had 64 data bits rather than 32.
> > > I had put 4 SDRAM chips on top and 4 on the bottom of the board,
> > > practically next to the CPU, no connectors between.
> > >
> > > Dimiter
> > >
> > > ------------------------------------------------------
> > > Dimiter Popoff Transgalactic Instruments
> > >
> > > http://www.tgi-sci.com
> > > ------------------------------------------------------
> > >
> > >
> > >
> > >
> > > -------Original Message-------
> > > > From: Aravnda G <aavinda12@xxxxxxxxx> > Subject: [SI-LIST]
> > > termination for routing 8 SDRAMs to single > Processor > Sent: Aug
> > > 11 '05 03:29 > > Hi All, > I am working with a micro-processor
> > > conneted to 8 SDRAM with 12 address lines to all SDRAMs and 32 data
> > > lines each to two sets of four SDRAMs. I was wondering if anyone has
> > > managed to route this sort of topology without using terminations. If
> > > so please send information on topology used. The IO are lvttl
> > > compatible at 3.3V. Any input on routing possibilities is welcome.
> > > >
> > > > Thanks & Regards,
> > > > Alex.
> > > >
> > > > ---------------------------------
> > > > Yahoo! Mail
> > > > Stay connected, organized, and protected. Take the tour > >
> > > ------------------------------------------------------------------
> > > > 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
> > > >
> > > >
> > > >
> > > -------Original Message-------
> > > ------------------------------------------------------------------
> > > 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
> > >
> > >
> > >
> > >
> > >
> > -------Original Message-------
> >
> >
> >
>-------Original Message-------
>------------------------------------------------------------------
>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
>
------------------------------------------------------------------
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:
