Minutes of SAS PHY Working Group conference call December2, 2010T10/11-013r0
Attendance:
Mr. Charles HillAlta Engineering
Mr. Mickey FeltonEMC
Mr. Douglas WagnerFCI
Mr. Vittal Batasubramanian FCI
Ms. Madhu RengarajanFCI
Mr. Fred FonsFoxconn Electronics
Mr. Barry OlawskyHewlett Packard Co.
Mr. Dan ColegroveHitachi Global Storage Tech.
Mr. Paul LarsonHitachi Global Storage Tech.
Mr. Scot BaumgartnerIBM Corp.
Mr. Mike OsborneIBM Corp.
Mr. Jay DiepenbrockIBM Corp.
Dr. Mark SeidelIntel Corp.
Mr. Joel SilvermanKawasaki Microelectronics
Mr. Harvey NewmanLSI Corp
Mr. Gabriel RomeroLSI Corp.
Mr. Paul WassenbergMarvell Semiconductor, Inc.
Mr. Kevin WittMaxim Semiconductor
Mr. Vasilis PapanikolaouMindspeed
Mr. Galen FrommMolex Inc.
Mr. Michael RostMolex Inc.
Mr. Chris ForeNetApp
Mr. Fred KnightNetApp
Mr. Mathieu GagnonPMC-Sierra
Mr. Alvin CoxSeagate Technology
Mr. Allen KramerSeagate Technology
Mr. Bruce JohnsonSeagate Technology
Mr. Mike FitzpatrickToshiba
Mr. Joel MeyersTycoElectronics
Mr. Dan GorencTycoElectronics
Mr. Scott ShueyTycoElectronics
Mr. Toney ChewVolex, Inc.
32 in attendance
Agenda:
SAS 2.1 public review comments
Went over the details of changes needed to resolve the public review comments. Two comments were received. Issues included the numbering on the QSFP+ connector illustration in figure 59, a sideband connection issue due to wrong pin numbering in the mini SAS to mini SAS HD cable in figure 70, and the line for SCD21 in figure 86 does not match table 23. Since updating figure 70 makes the pin assignments no different than shown in figure 71 except that the connector sides are swapped, this actually becomes a symmetric cable. The editor suggested that the text be updated to be like that for the symmetric cables already in the standard and that figure 71 be dropped. There was no one on the teleconference opposed to this change. The editor will document the updates and post for review on a teleconference December 9, 2010. After that review, the changes agreed to on that call will be put into a new revision of SAS 2.1 and that revision will posted after the teleconference. This will allow ample review time prior to the January plenary so that the updated standard can be voted on regarding a new public review.
SAS3_EYEOPENING update11-008
This presentation looks at a possible simulation software for SAS 3.0 modeling. It is similar to Matlab in its output. showing a difference between transfer function and simulated timecapture mostly below 3%. Frequency-domain transfer functions are accepted as input for through channel and crosstalk channels. For the crosstalk, NEXT and FEXT transfer functions can be entered. Still needs additional verification. A script is being validated and should be posted in the next couple of weeks for others to run verifications.
SAS multi-link signal/power noise simulation
Barry asked questions regarding the decoupling of the TxRx connection. The standard requires any transmitter or receiver that connects to SATA to have decoupling capacitors in both the transmitter and receiver paths since a SATA device may be DC coupled. A device that is only used in a SAS domain, such as a drive, is required to have decoupling caps on the receiver differential pair, but decoupling caps are not required on the transmitter pair.
Connectors and the reference channel
The following was posted to the T10 reflector regarding the connector situation and reference channel:
The drive connector mated pair was identified as an issue at 12G due to the crosstalk peaking near 6GHz. Simulations from multiple connector suppliers indicate that this peak can be moved to a higher frequency and thus, result in a connector mated pair enhanced to work at 12G.
Channel simulations on existing s-parameter files indicate that not all 6G channels are acceptable for 12G operation. I don’t consider this an unexpected result. 12G brings new challenges and it should be expected that optimization is needed to double the transfer rate. In an ideal world, all of these 6G channels should work at 12G, however, the added complexity, power, and expense of implementation does not necessarily support that goal with reality.
We have been looking at the 10 meter Mini SAS HD cable as the possible reference channel. There is confusion as to what the correct version is since there have been a few iterations of the HD connector design.
SAS 3.0 needs the reference channel defined so that we can move forward. Based on where we are at in the development and with the progress we have made as a group, I see the following as a minimum set of items we need to work on to move forward:
- Post a fresh set of Mini SAS HD cable s-parameters for 10 meter, 8 meter, and 6 meter cables. This will make sure that the same set of parameters is being used and let us know if 10 meters is achievable. Some early investigation indicated that we may need to reduce the length to 8 meters. This will give us the data available to determine what the capabilities and trade-offs are.
- The drive connector mated pair simulations appear to be very similar. The means to achieve this performance has not been openly shared. If IP is involved, that can be resolved as a separate issue. We need to see actual test data that supports the simulation data. This means that real s-parameters from real hardware needs to be supplied. We should move forward with the simulated data in parallel with actual connectors being built to provide verification that the simulation results are actually achieved.
- The channel requirements should include more information than currently used for 6G. One thing mentioned during the last meeting was a crosstalk to insertion loss spec. Crosstalk is definitely a major consideration, but in simple terms, are we not talking about SNR? How should we address this? I believe it is the right direction, but what would be the best way to approach it from a specification standpoint?
Item 1: Molex intends to post a new set of cable data the week of 12/20.
Item 2: No disagreement was voiced. Requested that actual data from connectors be presented at the January meeting if possible.
Item 3: Maxim voiced concerns that for 6G, their experience was that channel analysis was rarely done by users. They indicated that we need to have an easy-to-use simulation tool, preferably one that could be used with CAD layout tool output, which would allow simulations prior to building actual hardware. This way the channel would more likely be acceptable for 12G operation. Transmitter training also introduces some new challenges. They planned to have an updated presentation ready for the next teleconference.
Next call December 9, 2010
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Webex information:
Topic: SAS-2.1 PHY WG
Date: Thursday, April 22, 2010
Time: 10:00 am, Central Standard Time
Meeting number: 826 515 680
Password: newsas