[PCB_FORUM] Re: Length matching for DDR - was - RE: Realer V6.01 Constraint Manager

Amen.

-- 
George Patrick
Tektronix, Inc.
Central Engineering, EDS Applications Support
P.O. Box 500, M/S 39-512
Beaverton, OR 97077-0001
* 503-627-5272 (voice)     * 503-627-5587 (fax)
http://www.tektronix.com    http://www.pcb-designer.com
 
"Off-Grid and Proud of it!"


-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Gerry Meier
Sent: Thursday, February 28, 2008 09:45
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Length matching for DDR - was - RE: Realer
V6.01 Constraint Manager


Can you guys take this off-line please

Gerry Meier, Sr. PCB Designer
Freedom CAD Services. Inc
Voice: (256)776-7470 or (603) 864-1350
Email:gerry.meier@xxxxxxxxxxxxxx
visit us at http://www.freedomcad.com
 
 
-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Austin Franklin
Sent: Thursday, February 28, 2008 11:42 AM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Length matching for DDR - was - RE: Re:Allegro
V6.01 Constraint Manager

Hi Richard,

> I gave you some examples and I gave you some reasons.  You said
> you were receptive to new ideas but apparently not.

Of course I'm open to new information/understanding and the ensuing
discourse, which is why I've spent the time to read what you wrote and
read
the information at the links you provided.  The examples you gave, so
far,
haven't provided any information that supported your claim for tighter
length match constraints for the T branches.  In fact, the TI reference
showed they were the same (though lacked any analysis or explanation for
where they got their numbers from).

> There is more to life than designing from timing diagrams, and
> simulations do not always simulate real life and definitely not EMC.

No doubt there is more to life than that but not when you need to
provide
proper constraints for high speed designs.

In my experience, simulators are quite good these days, especially for
SI
and high speed design (at least up to the low to mid GHz which is the
limit
of my experience).  If an SI simulation is inaccurate, and you're using
a
good simulator, there is something wrong with the parameters of the
simulation.

> I think you have to be careful giving advice on tolerances.

I agree and I am ;-)

I don't really want to argue, that's not the point.  I just want the
information presented to be substantiated and accurate, and if it isn't,
to
know that as well.  No matter the source of the information.

Regards,

Austin

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