[BP] Parameter input to signaling spreadsheet

[Joe M Abler <abler@xxxxxxxxxx>]

Here's my input on the signaling comparison spreadsheet, specifically for the "Source Data Parameters" section.

On existing entries:

• My suggestion for Data Pattern is to use a random stream.
• Launch amplitude should be the minimum value proposed to the standard for the particular signaling method.
• Tx jitter should be split into both DJ and RJ, and should be set to the worst case value proposed to the standard for the particular signaling method.
• Tx jitter should also include worst case DCD.  This would go hand in hand with a statement that all simulators account for what's been termed phase noise amplification.  If that's not accounted for by all, then it should be excluded by all such that we have equivalent comparison.
• Rx allocated jitter should also identify both DJ and RJ.  I would suggest that the worst case values proposed by an implementation be used.  This would likely lead to different values being used in different simulations, and these differences would need to be accounted for in the complexity section (i.e. a design with a significantly lower RJ would be a higher power design).  If this second order comparison is expected to be too difficult, then we should plan to use common values.  Note that the current spreadsheet lists entries for Rx Input DJ & RJ.  I find the term "Input" a bit confusing since it could imply that it is the jitter seen at the input to the receiver (which is of course determined by the Tx jitter and the channel), but I assume this is meant to be the same as what I'm calling Rx allocated jitter, which is the amount of jitter associated with the receiver design, clock generation, etc.
• AC/DC coupling.  I would say we need someone to contribute a set of s-parameters for the AC coupling section of an actual design.  If that's not available in the short term, then I would suggest we not hold up simulations waiting for it.  I don't believe that excluding it would affect the signaling decision.  We still will need to have this eventually since it's effect needs to be accounted for in setting the normative channel model.
  
  Entries which I suggest be added:
  • Termination tolerance skew.  Should be set to worst case skew proposed to the standard for the particular signaling method.
  • Tx & Rx IC models.  Either need to agree to a common model or some measure of accounting for complexity.  Should not be using an ideal model.  
  • Tx launch signal.  This goes somewhat hand-in-hand with the Tx IC model.  If we have a realistic model, then it would be reasonable to use a square wave input.  If we end up with an ideal IC model (which I wouldn't recommend), then we should at least be using a slew-rate limited launch signal.
  • Receiver frequency offset.  Should be set to worst case proposed to the standard for a particular signaling method.
  • Receiver minimum latch overdrive value.  I suggest 15mV.
  • Common package model is needed.
  • Simulation time, in terms of number of bits, should be common.  I suggest 10M bit times to properly account for xtalk.
    
    And then final input is on the channels themselves.  I believe we should exclude any channels from the simulation set that don't include xtalk because with it they are simply too incomplete to be included in the decision making process.
    
    
    
    Thanks,        Joe
    
    
    Joe Abler                                                             abler@us.ibm.com
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