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formal apology

I apologize for any offense taken , none was intended. 
I did not intend to offend Mr. Widmer.  8B10B was
used successfully in the past and IBM was gracious
and fair in licensing 8B10B,  sorry again.

My out of place remark, was a lame attempt in light humor
and was not intended as a professional remark.
So please take no offence , none was intended.

At 01:20 PM 6/3/99 -0400, mwsachs@xxxxxxxxxx wrote:
>You owe Mr. Widmer an apology.  Unprofessional remarks such as yours are 
>out of place in an open standards body.  You should also know that the 8-10 
>has been part of Fibre Channel for nearly 10 years and there have never been 
>remarks about licensing.  Al Widmer's professional advice has also been
part of
>Fibre Channel for the same period and he is well respected by everyone
>with transmission codes.  IBM licenses its intellectual property for ANSI and
>IEEE standards according to the standards body rules as do many other 
>Martin Sachs
>IBM T. J. Watson Research Center
>P. O. B. 704
>Yorktown Hts, NY 10598
>914-784-7287;  IBM tie line 863-7287
>Notes address:  Martin W Sachs/Watson/IBM
>Internet address:  mwsachs @
>Haim Shafir <hshafir@xxxxxxx> on 06/03/99 11:33:05 AM
>To:   Albert X Widmer/Watson/IBM@IBMUS, rtaborek@xxxxxxxxxxxxxxxx
>cc:   Mark Ritter/Watson/IBM@IBMUS, John Ewen/Watson/IBM@IBMUS, Dennis L
>      Rogers/Watson/IBM@IBMUS, Mehmet Soyuer/Watson/IBM@IBMUS, Mounir
>      Meghelli/Watson/IBM@IBMUS, Martin W Sachs/Watson/IBM@IBMUS,
>      stds-802-3-hssg@xxxxxxxx
>Subject:  Re: [Fwd: 1000BASE-T PCS question], Importance of DC Balance
>And we can safely assume that IBM's ownership of the
>8B/10B patent does not impact you professional
>opinion at all.
>At 08:54 AM 6/3/99 -0400, widmer@xxxxxxxxxx wrote:
>>How important is DC Balance? This question is best answered by the engineers
>>design the critical three circuits (Laser Driver, Receiver Preamplifier,
>>Recovery), the persons who package the electrical and optical components, and
>>those who design the verification and production tests. Given an option, they
>>generally prefer a code with DC balance and a short run length. After
>>consultation with colleagues active in those endeavors, I can offer the
>>following list of circuit related advantages of a transmission code such
>as the
>>Fibre Channel 8B/10B code:
>>   Level settings of the laser driver bias point  and the receiver threshold
>>   be based on the average signal level which is simpler and more precise
>>   using level restoring circuits. The receiver level restore circuits
>>   require some type of peak detection circuits which are difficult to
>>   if the electronics is pushed to its limits. Peak detector noise may cause
>>   higher noise levels than otherwise expected because of the peak detectors
>>   tendency to capture occasional large noise excursions. The design of a
>>   detector which is both accurate and fast requires difficult inherent
>>   compromises.
>>   Thermal cycling of lasers or LED's is eliminated.
>>   Capacitive coupling  and level shifting is possible without
>complications to
>>   accommodate various package, grounding, and power supply configurations at
>>   the transmitter or receiver. At frequencies above 5 GHz it is hard to find
>>   capacitors which work well with unbalanced bit patterns for various
>>   Capacitive differential coupling at the front end of optical receivers
>>   small integrated capacitors is more easily accomplished and provides
>>   noise margins. At the lower data rates, designers may still include offset
>>   compensation circuits with a balanced code to reduce the capacitance
>>   to a range compatible with integration in monolithic circuits. Such
>>   compensation circuits require less precision and complexity for a balanced
>>   code.
>>   Receivers at the end of computer or LAN links generally require a large
>>   dynamic range which is more readily achieved with a balanced code.
>>   Attenuation in electrical package interconnects is on the order of 1
>>dB/cm at
>>   the fundamental frequency of 10 GHz and much higher for the frequencies
>>   needed to transmit fast pulse edges. Any transmission line is easier to
>>   equalize for balanced codes because of the lower ratio of the maximum to
>>   minimum frequency content.
>>   It is desirable to set the low frequency cutoff of receivers as high as
>>   possible to remove noise from several   sources, such as: power supply
>>   low frequency modal noise arising from movements of multimode fibers,
>or 1/f
>>   noise of front end devices, especially GaAs devices not optimized for low
>>   noise analog operation . For low and moderate cost highly integrated
>>   it is usually not possible to pick the best devices which otherwise
>might be
>>   used.
>>   The shorter run length of a good code allows much relaxed
>specifications for
>>   the clock recovery circuit. The lower Q of the PLL enables it to cope with
>>   more external noise interference such as digital noise coupling from
>>   neighboring circuits, power supply variations,  or totally external
>>   electromagnetic interference. It is less problematic to place a  PLL
with a
>>   lower Q on a large digital chip with limited isolation for a fully
>>   solution. The low pass filter of the PLL is more readily implemented
>with an
>>   on-chip capacitor or a totally digital solution (random walk filter)
>and the
>>   phase comparator is simpler for the coded version.
>>   For links carrying scrambled traffic, the link jitter budget expressed
as a
>>   percentages of a baud interval  allows much less jitter for the
>>   which significantly complicates the design of the frequency
>synthesizer, the
>>   laser driver, and the connection between the driver and the laser.
>>   Simpler circuits consume less power in a critical area.
>>   Scrambled data requires nearly ideal circuit implementations in the areas
>>   discussed above. Cost considerations, design time  and skill limitations
>>   the attainment of near perfection for the 10 Gb Ethernet application an
>>   unrealistic goal. Less than perfect circuits have a greater hidden cost in
>>   terms of signal to noise ratio for scrambled data. For a given baud and
>>   rate, the coded link can span a longer distance with less sophisticated
>>   circuits.
>>   The design, performance simulation, test, and trouble shooting is
>>   for a well constrained code. The robust operation of the coded link
>>   on no assumptions about the data pattern of the traffic. The
>performance can
>>   be proven with a few well defined worst case patterns tailored for
>>   the major performance parameters. There is no exposure to hacking via the
>>   data pattern. This is in contrast with scrambled links for which
>>   in practice  can only be verified for a statistical consensus pattern and
>>   where it is always possible to come up with data patterns which cause the
>>   system to fail.
>Haim Shafir
>e9 Inc.
>PH 408-343-0192 cell 408-892-1838 fax 408-873-2642

Haim Shafir
e9 Inc.
PH 408-343-0192 cell 408-892-1838 fax 408-873-2642