SAS PHY teleconference this FRIDAY, 6/23, 10 am CDT
Alvin.Cox at seagate.com
Alvin.Cox at seagate.com
Wed Jun 21 14:25:30 PDT 2006
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1. Training sequence/speed negotiation and SSC
Discussed Robâs 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 todayâs 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:
Â· Should SSC be on or off during receiver equalization setting?
Â· 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.
Â· 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.
Â· It is assumed that all expanders and initiators are capable of
receiving downspread SSC. Are there any know exceptions?
Â· Will an initiator or expander accept downspreading from a SAS
device running at G1 or G2 speed?
Â· 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).
Â· 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
PARTICIPANT CODE: 3243413
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
Seagate Technology, LLC
E-Mail alvin.cox at seagate.com
More information about the T10