Wide Links and Wide Ports

Sheffield, Robert L robert.l.sheffield at intel.com
Tue Feb 25 09:55:14 PST 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* "Sheffield, Robert L" <robert.l.sheffield at intel.com>
*
David,

You are correct that only one data transfer can be in progress for a given  I_T_L_Q nexus at a time (special exception for bidirectional cmds), but many I_T_L_Q nexuses can be active at the same time and use connections in a wide link as available. So a given I_T can have traffic in parallel on parallel connections, only each connection on the wide link carries traffic for a different L_Q nexus.

Bob
-----------------
Sent from my BlackBerry Handheld.

-----Original Message-----
From: David Freeman <david.freeman at datatransit.com>
To: t10 at t10.org <t10 at t10.org>
Sent: Mon Feb 24 18:27:24 2003
Subject: Re: Wide Links and Wide Ports

I guess that confusing part would be "A wide port shall only transmit DATA frames for a given I_T_L_Q nexus on one phy at a time" 
This seems to be saying that within a given I_T_L_Q nexus only one phy is in use at any given time. 
 
Does the wording of this section need to be clearer or am I misinterpreting this sentence?
 
David

----- Original Message ----- 
From: Seto,  <mailto:pak-lung.seto at intel.com> Pak-lung 
To: 'David Freeman'   ; t10 at t10.org 
Sent: Monday, February 24, 2003 5:03 PM
Subject: RE: Wide Links and Wide Ports

No, it explained very clear in the standard as you quoted in your email.  It can even use different PHYS.  The only requirement is that you can not switch link until all the data frame has been acknowledged.  You can even transmit and receive on two different links within the wideport.
 
Pak

-----Original Message-----
From: David Freeman [mailto:david.freeman at datatransit.com]
Sent: Monday, February 24, 2003 4:42 PM
To: t10 at t10.org
Subject: Wide Links and Wide Ports


I seem to be confused about how wide ports and wide links are handled. Section 8.3.3.1.4 of the SAS spec. (rev. D) says...
 
"  A wide port shall only transmit DATA frames for a given I_T_L_Q nexus on one phy at a time. The wide port may switch phys for DATA frames once all of the previous DATA frames have been acknowledged by the link layer. Read DATA frames and write DATA frames for the same I_T_L_Q nexus may be transmitted simultaneously and may be on the same or different phys."
 
Does this mean that inside a wide link all of the frames between and including the "Command" frame and the "Response" frame will only occur on one physical link?[Seto]  No 
 
This seems to defeat the purpose of having a wide link.
 
If there is any one out there that could help clear this confusion, I would appreciate it.
 
Thank You 
 
David R. Freeman
Data Transit


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