SAS PHY teleconference this FRIDAY, 6/23, 10 am CDT

Alvin.Cox at Alvin.Cox at
Wed Jun 21 14:25:30 PDT 2006

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1.	Training sequence/speed negotiation and SSC

Discussed Rob’s updated proposal that includes a shift in position on SSC 

method plus adds spec details for other areas that will need to be 

updated. A follow-up teleconference will be held on June 23 to continue 

discussing the proposal. Special items discussed during today’s call:

End devices only need to transmit with downspreading.

All receiver devices need the ability to accept center spreading, down 

spreading, or no SSC.

The G3 window is proposed as the last window for speed determination. If 

nothing happens during that window, the previously negotiated window  (G1 

or G2) is the speed. The G3 window would be run at 1.5 Gbps and include 

data transfer at the end to communicate speed and SSC capability and 

possibly other information. This would allow the next window to be the 

final speed negotiation window with receiver equalization tuning (G3 and 

faster). We discussed when SSC should be turned on. Although easier to 

turn on prior to tuning the receiver device, it may be preferred to turn 

on afterwards. Items needing investigation/comment:

·	 Should SSC be on or off during receiver equalization setting?

·	 Is it viable to make a drive have independent SSC control on the 

transmitters of its two ports? Independence is required to set the 

receiver equalization without SSC since one port may be operating prior to 

the other one performing speed negotiation.

·	 In the beginning of the final speed negotiation window, does there 

need to be an idle time or can both devices immediately start transmitting 

the training pattern? It is assumed that if G2 is required, the sequence 

would follow the SAS 1.1 standard.

·	 It is assumed that all expanders and initiators are capable of 

receiving downspread SSC. Are there any know exceptions?

·	 Will an initiator or expander accept downspreading from a SAS 

device running at G1 or G2 speed?

·	 If a phy transmitter has SSC disabled or is using downspread SSC 

only, it could get away with inserting fewer ALIGNs - 1/128 (the SATA 

ratio) would cover sending to either SAS or SATA phys with downspread SSC. 

Is that complication worth a 0.8% performance improvement? (e.g. at 6 

Gbps, this is 4.77 MBps).

·	 Rob will contact Harvey Newman to work on the speed negotiation 

window. Please note any special requirements that may be needed.

If at all possible, it would be of great benefit to have the SSC and speed 

negotiation sequence resolved at the July T10 meeting by completing 

updates to 06-263 and 05-397. These items are the most critical as they 

impact ASIC design. Other specification issues are likely to be controlled 

by adjustable parameters while these issues likely affect basic hardware 


2.	Next conference call June 23, 2006 


Toll Free Dial in Number: (866) 279-4742 

International Access/Caller Paid Dial In Number: (309) 229-0118 


Webex information: 

Topic: SAS-2 PHY WG 

Date: Friday, June 23, 2006 

Time: 10:00 am, Central Daylight Time (GMT -05:00, Chicago) 

Meeting number: 826 515 680 

Meeting password: 6gbpsSAS

Alvin Cox

Seagate Technology, LLC

Tel 405-350-7424

Cell 405-206-4809

E-Mail	alvin.cox at

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