[SI-LIST] Re: DDR SDRAM signal routing

  • From: Mike Brown <bmgman@xxxxxxxxxx>
  • To: mwmayer@xxxxxxx
  • Date: Mon, 08 Nov 2004 20:02:47 -0600

My experience is that very few products will gain a noticeable (or marketable) 
performance increase by pushing the envelope in the area covered by ap notes.  
If you are counting on product performance as a product differentiator, at that 
level, you are likely to lose market share while you are tweaking the design.  
Not to say that the ap note should be the final arbiter of what you put in your 
system, but you need a clear idea of what going outside the ap note is really 
buying (or costing.)  Particularly in the TTM dimension.


Mike Mayer wrote:

> Well, to take the devil's advocate position one step further,
> If I am a manager and my products have interfaces that are done "to the
> app note", is my company doing "engineering"? I can hire people cheaper
> than engineers that can read an app note and hook the chips together in
> a schematic editor.
> If you want to compete on more than cost (or cut costs by eliminating
> layers, etc.) you need to push the envelope of the design (i.e.,
> engineer) If you are pushing the envelope you are going beyond the app
> notes, and will get into trouble if you don't simulate.
> Just my opinion.
> On Mon, 2004-11-08 at 12:11, Tom Biggs wrote:
>>I'm going to play devil's advocate here just to get people thinking.
>>(Note that I simulate the DDR designs I've done).
>>Ed says "The driving force behind all this is time to market and system
>>There is one other force: cost. These days we can be easily outsourced
>>if we are too expensive to our bosses.=20
>>How many IBM PowerPC 440GX (now AMCC's chip) designs have been done? How
>>many times have people simulated them and come up with design guidelines
>>that will work? Yes, many of these designs are different from each
>>other, but I would bet that many of them are EXACTLY the same. Do we
>>need 100 engineers to simulate the exact same thing 100 times to come up
>>with 100 identical sets of routing rules?=20
>>If AMCC ran lots of simulations, then came out with a set of strict
>>routing rules for some typical embedded 440GX applications, then someone
>>should be able to design a board with these rules and not have to run
>>simulations. Reliability should be fine if they do their job right, time
>>to market will be short, and cost will be low.
>>    -tom

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