1. OPENING REMARKS Larry Lamers, the chairman, called the meeting to order at 9:00 a.m., Monday January 8,1990. He thanked Robert Snively of Sun Microsystems for hosting the meeting. As is customary, the people attending introduced themselves. A form was provided to generate a list of attendees. For the benefit of those attending the Ad-hoc Cable Working Group meeting for the first time the chairman outlined the objectives of the group. The objective is to discover and define the appropriate parameters for cables used to integrate SCSI systems. The cable specifications in SCSI-1 have proved to be less than adequete in fully loaded systems. Extensive work has been done by HP and Sun Microsystems testing cables. As a result of this testing it has been decided that the current specifications may need revision and additional parameters may need to be specified. 2. ATTENDANCE Meeting Attendees Name Stat Organization ------------------------------ ---- ------------------------------ Mr. Edward Bright V Mr. Allen Haigh V Ms. Nancy Waterman V Mr. Scott Ellis V Mr. Dan Hyer V Mr. James Fiala V 3M Mr. Denis D. Springer O 3M Company Mr. Bob Whiteman A AMP, Inc. Mr. Peter M. Blackford P Astro Cable Company Mr. Thomas Debiec O Belden Wire & Cable Mr. John A. Gibson P Berk-Tek, Inc. Mr. Wills Xu O C&M Corp. Mr. T. S. Lee V DTC Mr. John D. Walden P E.I. DuPont Inc. Mr. Stephen L. Clark A E.I. DuPont Inc. Mr. Bob Thornton O Fujitsu Components of America Mr. Terry Maezawa O Furukawa Electric Amer, Inc. Mr. Kurt Chan P Hewlett Packard Co. Mr. David McFadden P Honda Connector Mr. Hubert Lee V IBM Corp. Mr. Chuck Grant O Madison Cable Corp. Ms. Heide Wilson V Marketing Solutions Mr. Richard Wagner O Montrose Products Company Mr. Jim Giusso V Nicor Mr. Gene Milligan O Seagate Technology Mr. Robert N. Snively P Sun Microsystems, Inc. Mr. Vit Novak O Sun Microsystems, Inc. Mr. Armando Pauker V Tandem Mr. Duc Pham P Tandem Computer Inc. Mr. Kenneth Plourde O Tempflex Cable Inc. Mr. Warren Persak V Tempflex Cable Inc. Mr. D. W. Spence P Texas Instruments Mr. Harvey Waltersdorf P Thomas & Betts Mr. Keith Bean A Thomas & Betts 3. DOCUMENT DISTRIBUTION Documents distributed at the meeting will be included in the next X3T9.2 mailing. 4. WORK ITEMS 4.1. Measurement Methods Jim Fiala made a proposal for cable testing methods. If you accurately measure capacitance and propagation delay impedance can be calculated. This calculated impedance closely matches the end termination resistive measurement. The TDR has much lower accuracy when measuring impedance. John Gibson sent out a proposed measurement technigqe for checking crosstalk on differential cables Chuck Grant has prepared a test measurements method for single-ended cable. 4.2. Impedance Measurements Kurt Chan compiled impendance data report at plenary. Simulations indicate the differences of 25 ohms are significant. 4.3. Crosstalk Measurements 4.3.1. John Gibson reported that testing of differential cables did not indicate that cross-talk impacted the data reliability. John Gibson and Chuck Grant will look at single-ended cables for cross talk measurements. 4.3.2. Vit Novak reported on his testing of crosstalk in high density cables, in a fully loaded, full length cable. The testing was done on an emphirical basis. There are influeances due to mutual and intrinsic capacitance. Low skew seems to be more important than impedance in determining which cable provides satisfactory results. He asked what the relationship is between crosstalk and skew. Cross talk does not seem to be data pattern sensitive (data patterns of 00,FF, and 00 were tested). The criterea used was the minimum termpwr level at whick reliable data transfers could be made. The cables were grouped around 75 ohms and around 100 ohms. A write and compare of a six Mb file was done. There was no obserable difference in cables until terminators are de-coupled. The alternative one 220/330 termination was used. A given cable does not seem to be data pattern sensitive. However different cables had different Vterms at failure. Lower cross talk cables (50mv) failed at lower Vterms. Amoung lower cross talk cables the impedance did not make a difference in Vterm failure. There was higher cross talk at 150mv. The next step is to look at longer cables and with alternative two termination and check the long term reliablitiy. Asynch passes at Vterm of 4.25-5.0 volts. Synchronous mode failed at 4.6v, with no decoupling. The skew vales were taken from manufacturers specifications. 4.3.3. Jim Filia stated that low skew is due to better manufacturing control, which lowers crosstalk, but is skew is not related in an engineering sense to crosstalk. Bill Spence supported this with a statement that skew and cross-talk are not related, however the layout of the data lines in a round cable will affect cross-talk. Cross-talk is design engineering parameter, while the amount of skew is the result manufacturing control. 4.4. Nomographs Jim Filia gave a tutorial on cable problems. He recommended that attenuation and rise time specifications be added to document. Attenuation of voltage affects both the signal and the reflections and the cross-talk. Rise time degradation has an affect on uncertainty of signal level. Signal grounds and shield should be de-coupled to avoid two different propagation delays. 4.5. Marketing Issues The chair raised the issue of whether or not this ad-hoc meeting desired to make recommendations to the X3T9.2 plenary regarding the specifications currently in the SCSI-2 document. He advised them that the current public review comment period would close on February 16, 1990, and changes to SCSI-2 may be impossible to achieve after that date. The cable suppliers were asked what if they were feeling any marketing pressure to supply SCSI-2 compliant cables. The response was that so far they were dealing with the OEM market which was capable of making decisions on cable requirements that guaranteed system integrity without the help of a standard. However, they as the secondary market develops there will be a demand for SCSI-2 compliant cables. 4.6. System requirements Jim Filia stated that the system requirements need to be defined as well as the cable specifications if data integrity is to be insured. He is willing work on establishing the system requirements and invited systems integrators to participate. 5. RECOMMENDATIONS 5.1. That the 90 ohm requirement not be a 'shall' requirement in SCSI-2. 5.2. That warnings to implementors be increased awareness of attenutation, rise time and noise parameters that impact cable performance and reliabitlity. 5.3. Clarify in SCSI-2 that the AWG 28 diameter requirement should apply to termpwr and that the 90 ohm characteristic impedance applies to signal pairs. 6. MEETING SCHEDULE The next meeting of the Ad-hoc Cable Working Group is set for 9:00 am, March 5, 1990 at the Red Lion Inn in Costa Mesa, CA. The meeting is hosted by WESTERN DIGITAL CORPORATION. LOCATION: Red Lion Inn 3050 Bristol Street Costa Mesa, CA (714) 540-7000 ROOM RATE: $75.00 Single, $80.00 Double GROUP NAME: WD/SCSI RESERVATION CUTOFF DATE is February 28, 1990