> From: Koen Segers > Sent: Monday, May 07, 2007 12:49 PM > To: [EMAIL PROTECTED] > Subject: [ofa-general] DDR and SDR > > A simple question: > > Is it possible to connect a SDR HCA to a DDR switch?
Yes, at the time of Link Layer training, the link speed and width are negotiated down to the highest common speed/width. Hence when an SDR HCA is connected to a DDR switch, the HCA's link and the corresponding switch port will run at SDR speeds. > If so, what happens with the data that is send from a DDR HCA to the SDR > HCA? In IB every Path Record, Multicast group and Address Vector has a "static rate". This represents the speed of the path between 2 nodes. When a DDR HCA sends to an SDR HCA, it should have obtained a static rate from the SA showing a 10Gb/s rate (for a 4x SDR path). In which case, the DDR HCA will pace its sending to not exceed SDR speeds. Todd Rimmer Chief Architect QLogic System Interconnect Group Voice: 610-233-4852 Fax: 610-233-4777 [EMAIL PROTECTED] www.QLogic.com _______________________________________________ general mailing list [email protected] http://lists.openfabrics.org/cgi-bin/mailman/listinfo/general To unsubscribe, please visit http://openib.org/mailman/listinfo/openib-general
