Next Generation SPI WG Minutes

Lohmeyer, John JLOHMEYE at cosmpdaero.FtCollinsCo.NCR.COM
Fri Mar 17 17:42:00 PST 1995

Minutes of Next Generation SPI Working Group in Newport Beach, CA 

Accredited Standards Committee
X3, Information Technology
                                                   Doc. No.: X3T10/95-172r0
                                                       Date: March 17, 1995
                                                  Ref. Doc.:
                                                   Reply to: John Lohmeyer

To:                Membership of X3T10

From:              Ralph Weber, Secretary X3T10
                   John Lohmeyer, Chair X3T10

Subject:           Minutes of X3T10 SCSI SPI Futures Ad Hoc Meeting
                   Newport Beach, CA -- March 6, 1995



1. Opening Remarks

2. Attendance and Membership

3. Next-Generation SPI

4. Adjournment


                                 Results of Meeting

1.    Opening Remarks

John Lohmeyer, the X3T10 Chair, called the SPI the meeting to order at 9:10 
He thanked Skip Jones of QLogic for arranging and hosting the meeting.  The
meeting was held at the Hyatt Newporter, Newport Beach, CA.

As is customary, all those present introduced themselves.  John noted that 
meeting is an ad hoc meeting of the X3T10 committee.  John reminded everyone 
the X3T10 rules and noted that votes taken at this meeting (if any) have no
binding effect on X3T10.

2.    Attendance and Membership

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

The following people attended the meeting:

         Name          S        Organization         Electronic Mail Address
 ---------------------- -- ------------------------- 
Mr. Ron Roberts        A  Apple Computer            rkroberts at
Mr. Dennis R. Haynes   P  Burr-Brown Corp.          haynes_dennis at
Dr. William Ham        A# Digital Equipment Corp.   ham at
Mr. Ralph O. Weber     A# ENDL Associate            roweber at
Mr. Zane Daggett       O  Hitachi Cable 
            74354.2576 at
Mr. Dean Wallace       P  Linfinity Micro
Mr. Peter Gossler      O  NSM Jukebox GmbH 
         73503.3467 at
Mr. Skip Jones         P  QLogic Corp.              sk_jones at
Mr. Doug Prins         A# QLogic Corp.              d_prins at
Mr. Ting Li Chan       A  QLogic Corp.
Mr. James McGrath      P  Quantum Corp.             JMCGRATH at QNTM.COM
Mr. Gene Milligan      P  Seagate Technology 
       Gene_Milligan at notes.seaga
Mr. Stephen G. Finch   P  Silicon Systems, Inc.     5723283 at
Mr. Erich Oetting      P  Storage Technology Corp. 
 Erich_Oetting at
Mr. John Lohmeyer      P  Symbios Logic Inc.        john.lohmeyer at
Mr. Paul D. Aloisi     P  Unitrode Integrated       Aloisi at
Mr. Tak Asami          A  Western Digital           asami at

17 People Present

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

3.    Next-Generation SPI

Paul Aloisi reminded the group of the list of potential SPI futures topics:

    1. Incremental and/or replacement standards documents
    2. Connectors (32-bit, ..., high-density)
    3. Higher speeds
    4. Lower voltage
    5. Lower power
       a. termination
       b. silicon power for differential
    6. Hot swap (tm?) ... further definition
    7. System considerations
    8. Ease of use
    9. Cable specifications
   10. Backplane specifications
   11. Alternate topologies (bridges, routers)
   12. Enhanced error detection/correction
   13. Adaptive performance
   14. Fair access
   15. TERMPWR distribution
   16. Shield effectiveness
   17. Longer cable lengths
   18. High density external connector

John noted that a significant question is whether the next SPI document will 
a replacement for or addition to the existing SPI document.

John noted that Jim McGrath is advocating bridges and routers, particularly 
transaction processing systems.  Steve Finch raised concerns about low power
differential (which caused the minutes to divide item 5 into a and b).  The
problem with low-power differential is backwards compatibility.  Several
electrical issues including termination, cable impedance, and common mode
voltages prevent backwards compatibility in low-power differential.

Bill Ham asked for volunteers to work on low-power differential.  He did not
get a rousing show of support.  John did note that a repeater design might 
the interoperability solution for low-power differential.  Ralph postulated
that backwards compatibility is not really an issue.  The gains might be
sufficient to get people to make a non-compatible change in hardware.

During a discussion of cable length, it was noted that arbitration rules 
to change to permit cable lengths much in excess of 25 meters.  The signal
settling times must be increased to allow arbitration signals to transit the
longer cables.

The meeting next turned to issues of impedance and wire gauge.  Higher
impedance is needed to improve signal quality.  Thinner wires (larger wire
gauges) make the cables easier for people to handle and increase impedance.

Bill noted that the limits are lack of silicon and a defined termination
scheme.  The other key issue is accepting the choice for no backwards

Paul Aloisi presented a proposed differential termination circuit that John,
Bill, and Paul discussed in detail.  The circuit reduced the d.c. power
consumed by differential drivers without increasing the a.c. impedance.

Bill turned the discussion to 32-bit wide operation.  The main problems 
to be the cable and connector(s) required.  John noted that some of the 
proponents were planning on backplane implementations, which would not have
cable problems.  It was noted that 32-bit cables cannot accept 32 devices, 
to loading problems.

Bill suggested adding "Reserved line definition" as a SPI futures topic 
Bill suggested that at least some reserved lines would be needed for 
terminator power.

Eventually, Bill volunteered to lead a discussion to summarize the ideas
expressed.  With Bill's help, the group generated the following list of 
for SPI-of-the-future:

   - + performance parity with differential
       ++ length, device count, speed
     + cost parity with single ended
     = Single chip differential
   - Higher peak bandwidth
   - New devices capable of operating either
     low-power differential, or single-ended
     (a.k.a. backwards compatibility with old single-ended)
   - Backwards compatibility with old differential
     + cables, connectors, old devices the same (terminators different)
     + message protocol compatibility
     + arbitration protocol compatibility

Based on the above goals list, the group developed this following list of 
items as the core focus for SPI-2:

   - Low power chips
   - Alternate differential termination
   - 32-bit (just how compatible is it?)
   - Fast 40

     - Bridges and repeaters are still valid
     - Smaller cables/connectors are ok
     - Status bus should still be compatible (if used)

Jim McGrath noted the need for a bus extender focus.  Bill and Jim agreed 
the bus extender focus could be undertaken as a separate study project.  Jim
felt that this is appropriate, because work on standards enhancements for 
extenders is a short-term work project.

Jim gave a presentation describing the needs for bus extenders.  He also 
the basic mechanisms that are needed for bus extenders.  Jim and Bill 
the details of the electrical needs for bus extenders.  In effect, Jim's bus
extender needs can be met by publishing a spreadsheet developed by John for
setting bus lengths based on various timing parameters.

Bill, Jim, and John agreed that the best format to publish the needed
information is a technical report.  A project proposal must be created for 
bus extender information technical report.  Jim will create a project 
for forwarding later this week.  John will provide Jim with a boiler-plate 
for generating the project proposal.  (Note: These two actions did not 
so the project proposal will be generated later.)

In the process of discussing Jim's other desire for more than bus-width 
of devices per bus, the group added mechanisms for this to the core features

The group discussed the entire list of projects.  Marking those that cannot
have a proposal ready by July and assigning persons to prepare proposals for
the others.

The marked-up list thus produced was:

        1. Incremental and/or replacement standards documents
    x   2. Connectors (32-bit, ..., high-density) [McGrath]
 a  +   3. Higher speeds [*bundled with 5b]
 b  +   4. Lower voltage [Aloisi]
        5. Lower power
 b  +      a. termination [Aloisi]
 a  +      b. silicon power for differential
 e  +   6. Hot swap (tm?) ... further definition [Aloisi/McGrath/Ham]
    x   7. System considerations
    x   8. Ease of use
 b      9. Cable specifications [*bundled with 15*]
    x  10. Backplane specifications
 c  +  11. Alternate topologies (bridges, routers) [Ham/McGrath/Lohmeyer]
    x  12. Enhanced error detection/correction
    ?  13. Adaptive performance [Lohmeyer]
    ?  14. Fair access [Penman]
 b  +  15. TERMPWR distribution [Ham]
 d  +  16. Shield effectiveness [Ham]
 c  +  17. Longer cable lengths {TechReport} [McGrath/Lohmeyer/Ham]
 d  +  18. High density external connector [SFF]
    ?  19. Reserved line definition [SFF]
 a  +  20. >16 devices addressable on the same logical bus [McGrath]
 a  +  21. Alternate differential termination [Aloisi]


 a High-Performance Server SPI
 b Portable SPI
 c Extended Topologies SPI
 d External Connections SPI
 e Hot Plugging
    + paper expected by July
    ? paper may be ready by July
    x no paper ready by July

4.    Adjournment

The meeting was adjourned at 5:30 p.m. on Monday March 6, 1995.

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