Minutes of SPI-2/EPI Working Group -- 7/15/96

Lohmeyer, John JLOHMEYE at cossymwest.co.symbios.com
Mon Jul 22 16:12:00 PDT 1996

* From the SCSI Reflector, posted by:

Minutes of SPI-2/EPI Working Group               X3T10/96-201r0

Accredited Standards Committee*
X3, Information Technology
                                    Doc. No.: X3T10/96-201r0
                                        Date: July 22, 1996
                                     Project: 1142-D
                                   Ref. Doc.:
                                    Reply to: John Lohmeyer

To:       Membership of X3T10

From:     Bill Ham, SPI-2 Technical Editor
          Ralph Weber, Secretary X3T10
          Larry Lamers, Vice-chair X3T10
          John Lohmeyer, Chair X3T10

Subject:  Minutes of SPI-2/EPI Working Group
          July 15, 1996 -- Colorado Springs, CO


1. Opening Remarks

2. Approval of Agenda

3. Attendance and Membership

4. Documentation Strategy [Lamers/Ham]

5. LVD Topics
  5.1   Test   Circuit  Considerations  for  Voltage  Mode  Drivers
  5.2 Standing Waves [Bridgewater]
  5.3 Should Fast-80 be included in SPI-2?  SUPR?  [Milligan]
  5.4 Fast-80 Deskew Delay [Moore]
  5.5 Hot Plugging [Bridgewater]
  5.6 Universal Backplane [Ham]
  5.7 SPI-2 Document Review (X3T10/1142D) [Ham]
  5.8 Fast-80 Test Results (96-200r0) [Ham]
  5.9 Frequency Range on Terminators [Schmalz]

6. High-Voltage Differential Fast-40 (96-190) [Gingerich]

7. EPI Topics
  7.1 Arbitration Fairness (96-172) [Lohmeyer]
  7.2 Document Review [Ham]

8. Universal Definition [Ham/Milligan]

9. Meeting Schedule

10. Adjournment

                          Results of Meeting

1.   Opening Remarks

John Lohmeyer, the X3T10 Chair, called the meeting to order at 9:03
a.m., Monday July 15, 1996.  He thanked Symbios Logic for allowing him
to host the meeting.

As is customary, the people attending introduced themselves and a copy
of the attendance list was circulated.

2.   Approval of Agenda

The agenda was approved with the following additions:

     5.8 Fast-80 Test Results [Ham]
     5.9 Frequency Range on Terminators [?]
     8. Universal Includes HVD [Ham]

3.   Attendance and Membership

Attendance at working group meetings does not count toward minimum
attendance requirements for X3T10 membership.  Working group meetings
are open to any person or organization directly and materially
affected by X3T10's scope of work.  The following people attended the

         Name          S        Organization         Electronic Mail
 ---------------------- -- -------------------------   
Mr. Norm Harris        P  Adaptec, Inc.   
            nharris at eng.adaptec.com
Mr. Lawrence J. Lamers A  Adaptec, Inc.             ljlamers at aol.com
Mr. Richard Moore      V  Adaptec, Inc.   
            richard_moore at corp.adaptec
Mr. Wally Bridgewater  V  Adaptec, Inc.             wally at eng.adaptec.com
Mr. Tom Schneider      V  Adaptec, Inc.   
            schneid at itc.adaptec.com
Mr. Louis Farshee      V  Aeronics, Inc.
Mr. Charles Brill      P  AMP, Inc.                 cebrill at amp.com
Mr. Ron Roberts        A  Apple Computer            rkroberts at aol.com
Mr. Borden Moller      A  CMD Technology            borden at cmd.com
Mr. Louis Grantham     P  Dallas Semiconductor      grantham at dalsemi.com
Mr. Siegfried Schmalz  V  Dallas Semiconductor      schmalz at dalsemi.com
Mr. Greg McSorley      O  Data General Corp.   
       greg_mcsorley at dgc.ceo.dg.
Mr. Roger Cummings     P  Distributed Processing   
   cummings_roger at dpt.com
Mr. Dean Wallace       P  Linfinity Micro   
          75671.3443 at compuserve.com
Mr. Pete McLean        P  Maxtor Corp.   
             pete_mclean at maxtor.com
Mr. Edward A. Gardner  P  Ophidian Designs          gardner at acm.org
Mr. Tom Jones          V  QLogic Corp.              t_jones at qlc.com
Mr. Gene Milligan      P  Seagate Technology        Gene_Milligan at notes.
Mr. Gerald Houlder     A  Seagate Technology        Gerry_Houlder at notes.
Mr. Dave Guss          P  Silicon Systems, Inc.   
    dave.guss at tus.ssi1.com
Mr. Robert N. Snively  P  Sun Microsystems Computer   
bob.snively at eng.sun.com
Mr. John Lohmeyer      P  Symbios Logic Inc.   
       john.lohmeyer at symbios.com
Mr. Ralph O. Weber     A# Symbios Logic Inc.        roweber at acm.org
Mr. Mark Jander        V  Symbios Logic Inc.   
       mark.jander at symbios.com
Mr. Frank Gasparik     V  Symbios Logic Inc.   
       frank.gasparik at symbios.com
Mr. Kevin Bruno        V  Symbios Logic Inc.   
       kevin.bruno at symbios.com
Mr. Brian Day          V  Symbios Logic Inc.        brian.day at symbios.com
Mr. Kevin Gingerich    O  Texas Instruments, Inc.   k-gingerich at ti.com
Mr. Paul D. Aloisi     P  Unitrode Integrated       Aloisi at uicc.com
Mr. Doug Piper         P  Woven Electronics         549.9900 at mcimail.com

30 People Present

Status Key:  P    -  Principal
             A,A# -  Alternate
             O    -  Observer
             L    -  Liaison
             V    -  Visitor

4.   Documentation Strategy [Lamers/Ham]

John reported on the history of the debate about the contents of the
SPI-2 document.  John focused on events that occurred during the last
two months.  There was a brief discussion of the political issues.
But, John asked that the discussion focus on technical issues and
recognize that the political debate will be held during the plenary.

John also reviewed the results of the recent STA meeting.  The STA
opinions on Fast-80, when to Migrate to Encoded SCSI, and Hot Plugging
were presented and discussed.  In summary, STA would like to see Fast-
80 and Hot Plugging case 4 work, but will accept other situations in
order to get LVD SCSI finished promptly.  STA postponed answering the
migration to encoded SCSI question.

5.   LVD Topics

     5.1  Test Circuit Considerations for Voltage Mode Drivers

Wally questioned the dynamic output signal balance test for LVD
drivers.  After some discussion, the group decided to add a note
allowing 120 mv peak-to-peak voltage for high-to-low and low-to-high
transitions; and 400 mv peak-to-peak voltage for transitioning into
and out of the high impedance state.

     5.2  Standing Waves [Bridgewater]

Wally stated that he has not been able to detect standing waves in his
testing.  The group agreed to drop this item from future agendas.

     5.3  Should Fast-80 be included in SPI-2?  SUPR?  [Milligan]

The group agreed that Fast-80 should be dropped from SPI-2.  It was
further agreed that Fast-80 should be included in a future document,
as appropriate.

     5.4  Fast-80 Deskew Delay [Moore]

Based on the decision to drop Fast-80 from SPI-2, concerns over the
Fast-80 deskew delay were thought to be academic.

     5.5  Hot Plugging [Bridgewater]

Bill Ham described a possible connector design that has split
contacts.  The inital lead-in portion of the contacts would have high-
impedance while the final portion would be low-impedance.  This
contact design could alleviate the spiking problems that occur in hot
plugging case four by allowing the contacts to charge at a slower
rate.  With single-ended, the signal levels were large enough to mask
the spikes.  LVD signal levels are much lower and could be adversely
affected by the spikes.

Another approach to reduce the problem would be to bias the contacts
to a voltage approximately half-way between the high and low signal
levels.  Bill noted that he believes that there is a patent on this
approach.  Bill is still investigating.   Both methods would require a
sequenced connector (i.e., one that has split contacts).

A simulated case four, with the software handling the bus interruption
also is possible.

     5.6  Universal Backplane [Ham]

Bill described the impedance issues related to building cables and
backplanes.  He described the impedance ratios that naturally occur in
cables, but do not occur in backplanes.  He then asked the group to
confirm that the needed ratios can be achieved on backplanes, and if
possible, to describe how to build such backplanes.  Dean Wallace
volunteered to run some sample calculations to demonstrate how
universal backplanes could be made.

     5.7  SPI-2 Document Review (X3T10/1142D) [Ham]

Mark Jander and Brian Day raised questions about the DIFFSENS circuit.
They noted that a 10% power supply combined with a voltage divider
would push levels in the circuit outside those shown in SPI-2, as
currently written.  This produced a lengthy discussion that resulted
in several changes to table 6.  The group then turned to the issue of
how devices should respond to change in the DIFFSENS line level.
While the discussion was lengthy, no substantial changes were made.

     5.8  Fast-80 Test Results (96-200r0) [Ham]

Bill Ham presented test data intended to provide guidance on the
standardization process to be followed for Fast-80.  Bill's data was
developed using symmetric transmitters and terminators based on
Fast-40 test transmitters provided by TI.

In summary, Bill noted that Fast-80 probably will not work on the same
cabling/protocol system as used by Fast-40.  Bill showed several
specific scope trace pictures proving his contention that changes
beyond just timing will be required to transition from Fast-40 to
Fast-80.  Bill noted that the major problem is ISI (inter-symbol
interference).  He expressed the belief that, if the ISI could be
reduced enough, Fast-80 could work made to work on Fast-40

Many questions were asked to help clarify Bill's views about issues.

Bill concluded that work on Fast-80 should be deferred to a future
document.  He further noted that Fast-100 should be the next goal.
Bill was asked what changes he expected to be needed for Fast-100.
Bill stated that more "clock like" REQ/ACK signals appear to be
necessary -- i.e., the REQ and ACK streams cannot be started and
stopped instantly as is presently the case.

     5.9  Frequency Range on Terminators [Schmalz]

Siegfried Schmalz of Dallas Semiconductor presented an analysis on the
frequency range of terminators.  Concerns were raised that the
parasitic capacitance will cause problems with meeting the terminator
requirements specified. The issue was the nature of the parasitic
capacitance when measured at request frequencies (120 Mhz).

What is the maximum parasitic capacitance at a given frequency that
can be allowed?  At 120 Mhz the calculations show that c1 and c2 are
0.7 pf and c3 is 0.3 pf.  Bill Ham suggested that a note be added to
table 7 stating that the requirements only apply to the real value
(not the imaginary value) when the measurements are made at frequency.
Another approach is to make table 7 DC numbers and allow looser AC

6.   High-Voltage Differential Fast-40 (96-190) [Gingerich]

Discussion of this topic was deferred to the next meeting.

7.   EPI Topics

     7.1  Arbitration Fairness (96-172) [Lohmeyer]

The proposal is a reintroduction of a 1989 proposal from IBM
(X3T9.2/89-061).  The proposal was not discussed in detail at this
meeting, however there was general agreement that it should be
documented in a future standard as opposed to a technical report.

     7.2  Document Review [Ham]

Bill Ham reviewed EPI rev 6.

8.   Universal Definition [Ham/Milligan]

Bill started the discussion by stating that connector definitions in
SPI-2 already coordinate with HVD (High-Voltage Differential) SCSI.
The SCA-2 connector has defined compatible pin-outs for single-ended,
HVD, and LVD SCSI.  Later In the meeting Bill was persuaded that while
a three-way universal backplane might be possible, other necessary
components to build a complete three-way universal system might be
impossible (at least practically impossible).  It was suggested that
the SPI-2 document references to devices that support both single-
ended and LVD should be changed from `universal' to `dual-mode' to
avoid the implication that HVD also is supported.

Gene Miligan expressed concern that building a universal driver that
meets the 20 pf will be difficult and may be impossible.  Ultimately,
this was a marketing discussion and no resolution reached.  Bill
Galloway said he would like to take an existing single-ended subsystem
and put universal drives in it, but fears that devices with more than
15 pf node capacitance will not work.

9.   Meeting Schedule

The next meeting of SPI-2 Working Group is scheduled for August 13-14,
1996 in Milpitas, CA hosted by Technology Forums.  Another meeting is
scheduled for September 9th in Natick, MA.  The group recommended that
October and December meetings be held with X3T11 on Thursday (October
10th in St. Petersburg Beach, FL and December 5th in Bloomington, MN).

10.  Adjournment

The meeting was adjourned at 7:30 p.m. on Monday July 15, 1996.

John Lohmeyer                 E-Mail: john.lohmeyer at symbios.com
Symbios Logic Inc.             Voice: 719-533-7560
4420 ArrowsWest Dr.              Fax: 719-533-7036
Colo Spgs, CO 80907-3444    SCSI BBS: 719-533-7950 300--14400 baud

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