[SI-LIST] Re: Fibre channel interconnect margins

  • From: David Instone <dave.instone@xxxxxxxxxx>
  • To: steve weir <weirsi@xxxxxxxxxx>
  • Date: Tue, 04 Jul 2006 11:10:29 +0100

   I didn't disallow an infinite time between events.  I allow for the 
time between events to be between 0 and infinity, but not negative.  
Thus if I'm measuring the time between edges and my reference I can 
measure an infinite time between my reference and a following edge but 
never more than 1 UI between the last edge and my reference.  That last 
edge could of course be from a edge that should have occurred an 
infinite amount of time in the future, but from the point of view of the 
measurement it's only 1 UI early.

steve weir wrote:
> David, I disagree.  It does not change causality.  It changes the 
> incremental delay between two events.  Imagine for a moment that we 
> have a simple relaxation oscillator as the basis of our VCO.  In the 
> presence of an infinitely large noise pulse, which is the limit for 
> random noise, it takes an infinite amount of time for the ramp to 
> reach the threshold.  The next cycle will not begin untilt he current 
> cycle completes.  It may sound like something from Douglas Adams, but 
> it really is mathematically and physically sound.
> Regards,
> Steve.
> At 01:50 AM 7/4/2006, David Instone wrote:
>> Because it makes for a nice simple clean definition.  However, I 
>> believe you have to take the real world into consideration.  Allowing 
>> the RJ to be really unbounded means that each edge in a bit stream 
>> could be advanced or delayed by an infinite amount.  Taken to 
>> extremes this means that  the order of  edges  could be reversed.  
>> This is obviously absurd, the measured time between edges can reduce 
>> until it is zero, it cannot go negative.  The time between edges can 
>> of course go to +ve infinity, but that isn't a bit error, the system 
>> has failed or been switched off.
>> steve weir wrote:
>>> RJ really is unbounded by definition.
>>> Steve.
>>> At 09:46 AM 7/3/2006, Steven Kan wrote:
>>>>> Date: Fri, 30 Jun 2006 21:48:56 -0700
>>>>> From: Alan.Hiltonnickel@xxxxxxx
>>>>> Subject: [SI-LIST] Re: Fibre channel interconnect margins
>>>>> In fact, I think that companies DO ship products that toss a random
>>>>> error approximately every 10e-xx or so. Why? Because the statistical
>>>>> theory behind those errors is that random/Gaussian noise is, by
>>>>> definition, unbounded - errors are a fact of life, even if the error
>>>>> rate is very low.
>>>> I suppose we're way off in the weeds, here, but is the noise actually
>>>> unbounded? Or does it just behave in a Gaussian-like manner within 
>>>> the realm
>>>> of times/rates that matter for shipping product? I suppose if I sat 
>>>> in my
>>>> chair for long enough, a truly unbounded system might cause a gold 
>>>> bar to
>>>> pop into existence on my desk, but my empirical GBR (gold-bar rate) is
>>>> currently 0.
>>>> ------------------------------------------------------------------
>> -- 
>> Dave Instone
>> Oxford Semiconductor Ltd
>> 25 Milton Park
>> Abingdon
>> Oxon ox14 4ea
>> UK
>> www.oxsemi.com
>> +44 (0)1235 824963

Dave Instone
Oxford Semiconductor Ltd
25 Milton Park
Oxon ox14 4ea
+44 (0)1235 824963

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