[SI-LIST] Re: DDR3-1600 Double-Tee Topology
- From: "Ghode, Nikhil" <Nikhil.Ghode@xxxxxxxxxxxxxx>
- To: "prashant.jaiswar@xxxxxxxxx" <prashant.jaiswar@xxxxxxxxx>, "Surjendra Goswami" <goswamisurjendra@xxxxxxxxx>, "brian.p.moran@xxxxxxxxx" <brian.p.moran@xxxxxxxxx>
- Date: Tue, 14 Jan 2014 18:45:43 +0000
Joseph,
I recently used T-topology for DDR3 routing, however I used only two memories
running at 400MHz clock. Hence I had plenty of timing margin.
If you planning to use T-topology then I would not recommend to use write
leveling. It is useful in flyby to compensate for delays.
It is important to check timing budget. Also check if you have enabled
terminations inside the DDR3 for write operation, you can also use dynamic
termination for write cycles.
Regards,
-Nikhil
Ph: 845-731-2277
Fax:845-731-2011
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Prashant Jaiswar
Sent: Tuesday, January 14, 2014 1:19 PM
To: Surjendra Goswami; brian.p.moran@xxxxxxxxx
Cc: josephaday@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: DDR3-1600 Double-Tee Topology
fly by topology is helpful in DIMM routing.
As Moran has mentioned it would be difficult to route double tee. This would
eat up your timing margins, you would need a careful simulation done. Write
leveling is a feature suggest to be used in DIMM type DDR3 memory
configurations.
Sent from my Windows Phone
From: Surjendra Goswami
Sent: 14-01-2014 23:24
To: brian.p.moran@xxxxxxxxx
Cc: josephaday@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: DDR3-1600 Double-Tee Topology Joseph,
DDR3 supports write leveling and hence the fly-by topology is the most
prolific an DDR3 designs.
The double tee topology was used for DDR2 and had some downside in the
impedance discontinuities due to branching along the routes causing obvious
margin losses.
Regards
Surjendra
On Tue, Jan 14, 2014 at 10:25 PM, Moran, Brian P <brian.p.moran@xxxxxxxxx>wrote:
> Joseph,
>
> I have seen the Tee-Tee or the hybrid Tee-Daisy topology used in some
> instances. You are correct that the Tee-Tee is a pain to route and
> usually requires a type 4 MB. We do employ it in some LPDDR3 memory
> down configurations. In either case, it does require some impedance
> compensation between the main trunk and the tee branches in order to
> optimize. This is different than the tree topology used in DDR2, in
> that the length to all loads is matched. Where we found the Tee-Tee
> particularly interesting is when using multi-die pkgs. The daisy
> chain topology does not work well with high capacitance loads, such as
> you can have with LPDDR3 DDP and QDP devices. You can get excessive
> ledging and ringback in the first few nodes in the daisy chain. This
> is the reason the Tee-Tee topology was developed. However, if you are
> supporting only SDP devices then the daisy chain is the most
> straightforward.
>
> Brian Moran
> Memory Interface Technology
> Client Platforms
> Intel Corporation
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Joseph Aday
> Sent: Monday, January 13, 2014 6:07 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] DDR3-1600 Double-Tee Topology
>
> Hi Everyone,
>
> Has
> anyone tried using a double-tee topology with their
> address/command/control signals in DDR3L/LPDDR3? This would be
> instead of the standard daisy-chain, with an Rtt at the end of the line.
>
> For example, take a controller with four memory nodes. It would look
> like this (think of DDR2 days):
>
> - RX
> - Branch -|
> | - RX TX ----------------- Rtt
> | - RX
> - Branch-|
> - RX
>
> To ensure matched timing for write leveling, this would even apply to
> the differential clock. I am doing memory-down (chips directly on the
> PWB as opposed to DIMMs.. if that matters?)
>
> Compared
> to a simple daisy chain, my simulations show this to be a bad idea
> both in eye diagram margins and in s-parameter plots. The double tee
> has less vertical / horizontal eye margin. The double-tee also has a
> resonant "suck out" in insertion loss very close to the clock
> frequency, whereas the standard daisy-chain is relatively flat out to 3GHz.
>
> Our
> chip vendor tells us this is needed to improve the eye diagram, but I
> can't see how or why. This is also a pain to route.. and so I have no
> good ideas as to why I should do this :)
>
> Am I missing something? Thoughts? Anyone else in the same boat? :)
>
> Thank you,
> Joseph Aday
> ------------------------------------------------------------------
> 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 forum is accessible at:
> http://tech.groups.yahoo.com/group/si-list
>
> List archives are viewable at:
> //www.freelists.org/archives/si-list
>
> 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 forum is accessible at:
> http://tech.groups.yahoo.com/group/si-list
>
> List archives are viewable at:
> //www.freelists.org/archives/si-list
>
> 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 forum is accessible at:
http://tech.groups.yahoo.com/group/si-list
List archives are viewable at:
//www.freelists.org/archives/si-list
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 forum is accessible at:
http://tech.groups.yahoo.com/group/si-list
List archives are viewable at:
//www.freelists.org/archives/si-list
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 forum is accessible at:
http://tech.groups.yahoo.com/group/si-list
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
