[SI-LIST] Re: NPU / DDR interface bug issue
- From: "BOUTHEMY JEAN PIERRE" <Jean_Pierre.Bouthemy@xxxxxxxxxxxxxxxxx>
- To: <crj@xxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 10 Apr 2007 17:38:32 +0200
Hi Chris,=20
The complete test procedure is the following:=20
1- I write some defined words in a defined memory space
2- I read this same memory space to make sure I find the value I wrote: =
it is always the case
3- I run the full bandwith test
4- When the test fails, I read the same memory space and I observe =
anythjing, but not the value I had written in the memory
I will try the "freeze spray" on the DDR.=20
Thank you,=20
Jean-Pierre
-----Message d'origine-----
De : si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
De la part de Chris Johnson
Envoy=E9 : mardi 10 avril 2007 16:36
=C0 : BOUTHEMY JEAN PIERRE; si-list@xxxxxxxxxxxxx
Objet : [SI-LIST] Re: NPU / DDR interface bug issue
When you say that the DDR is blocked, what do you mean? The interface =
is no longer working at all?
It is not unusual for a marginal problem to go away when you load the =
lines in question by probing them.=20
It could be that there is a meta-stable condition that is affected by =
the slight change (usually slowing down) of the bus signals caused by =
probing.
You can see if probing one particular line causes the problem to go away =
by removing probes until it stops working again.
Even with 3" wires, I'm not sure that your interface signals should look =
all that bad, so it could be a signal integrity problem as well.
You can try using a resistive probe so that the ground issues are not as =
much of a concern.
See http://www.sigcon.com/Pubs/news/5_4.htm .
You could also try spraying any suspect chips with "freeze spray" to see =
if the change in temperature also affects the problem.
If a cold chip runs better, that also implies that it is a timing issue.
Good Luck.
Chris Johnson
BOUTHEMY JEAN PIERRE wrote:
> =3D20
> Hello SI experts,
>
> I have to solve for a DDR interface issue when traffic is full=20
> bandwith
> (1Gb/s): DDR is then blocked and we can not access to it anymore.=3D20 =
> Note that this "should not be" a card bug because it happens only on a =
> few cards, about 2 or 3 protos among more than 100 cards.=3D20 FYI, =
the=20
> Controller is an Intel Network Processor IXP2400 and the DDR interface =
> is running at 150MHz.=3D20
>
> On one of the fail cards, I have soldered some wires (about 3" long)=20
> on a few signals (CS, WE, RAS, CAS, CK, DQS0 and DQ0) and attached 4=20
> probes on CK, WE, DQS0 and DQ0. I have launched the full bandwith test =
> on this card and observed that it is now running OK for more than 118=20
> hours without failing!!=3D20
>
> The scope signals are very poor on the scope (scope + probe bandwith >
> 6GHz) because of the too long wires and the ground connection which is =
> very poor.=3D20 But I can not understand why the interface is running =
OK=20
> for more than 5 days, whereas it normally fails before 2 minutes of=20
> full bandwith test!!
>
>
> Has someone already experienced such a case?=3D20 Could you please=20
> explain if some stubs on signals could make the signal integrity=20
> better, or ameliorates a timing, or so ...=3D20
>
> Please remember that only 2 or 3 cards among more than 100 have this=20
> issue, which means that it "should not" be a design issue.=3D20
>
> Thank you for your help,
> Regards,=3D20
>
> Jean-Pierre.=3D20
> ------------------------------------------------------------------
> 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 technical documents are available at:
> http://www.si-list.net
>
> List archives are viewable at: =20
> //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
> =20
>
>
>
> =20
------------------------------------------------------------------
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 technical documents are available at:
http://www.si-list.net
List archives are viewable at: =20
//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
=20
------------------------------------------------------------------
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 technical documents are available at:
http://www.si-list.net
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:
