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Samsung XS1715 1.6TB 2.5-inch NVMe PCIe Enterprise SSD Review

By: Paul Alcorn | PCIe SSDs in IT/Datacenter | Posted: Oct 23, 2014 2:30 pm
TweakTown Rating: 94%Manufacturer: Samsung

Page 3[SFF-8639 and ExpressBay]


SFF-8639 and ExpressBay




The Samsung XS1715 came to our lab with a PCIe card and custom backplane connected via three cables. This development kit is not used in actual deployments.




The PCIe card is simple, with three connectors for the wires that connect to the backplane. The cable to the left is a typical SAS cable, the middle cable is used for power delivery (the XS1715 uses 3.3v and 12v), and the cable on the right is a typical SATA cable, which might be used for refclock signals.




The backplane has mating connectors for the three wires on the back, and an SFF-8639 connector on the front.




SFF-8639 is a new connector that serves as the Swiss army knife of storage connections. SFF-8639 is a multifunction 6x unshielded connector defined by the SSD Form Factor Workgroup (SSD FFWG). SFF-8639 supports single port SATA, dual port SATA Express, dual port SAS, MultiLink SAS, and up to 4-port PCIe device configurations. Backplanes with this connector are compatible with plugs developed in accordance with SFF-8482, SFF-8630, and SFF-8680s specifications. The connector supports all of the pins for dual-port SAS, and adds an additional 39 pins to support four PCIe lanes and 10 sideband signals. 14 of the additional 39 pins are used for two additional SAS ports in MultiLink SAS connections.


In normal deployments, ExpressBay extends PCIe speed to the front panel and provides an easy connection for drives with the SFF-8639 connector. ExpressBay is a multi-protocol externally accessible storage slot that supports 2.5" or 3.5" devices compatible with the SFF-8639 connector. Standard drive bays are limited to 9 Watts of power, but ExpressBay bumps that up to 25 Watts - the same as the typical ceiling of a PCIe slot on the motherboard. Additional airflow is also provided for dissipation of higher heat levels.




SFF-8639 also brings hot-swapping capability to the PCIe interface. A closer examination of the plug interface reveals a 3-level contact engagement sequence. The mating sequence of the contacts is timed to occur in the proper order. This is accomplished through a carefully designed offset between contacts on each side of the plug and receptacle.




Dell utilizes PCIe extender adaptors to connect the PowerEdge R920's drive bays to the PCIe slots on the motherboard. The direct PCIe connection yields a maximum bandwidth of 8 GB/s.

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