Abstract:
A system for providing dual 10 GB uplinks in the front side of a single rack unit switch that stacks two MSA X2 I/O devices in a limited space. In one embodiment the two X2 I/O devices are mounted on opposite sides of a single circuit board positioned above the motherboard.

Description:
BACKGROUND OF THE INVENTION 
   Single rack unit (1 RU) switches, or pizza boxes, are ubiquitous in offices and businesses and there has been a push by manufacturer&#39;s to add more and more features while driving down costs. Current 1 RU switches provide 48 ports for connecting to end-devices. Additionally, the units must provide uplinks to connect to backbone or core routers or switches. Generally, two uplinks are required to provide redundancy. 
   The dimensions of the front face of a single RU switch are only 1.75″×17.5″. The actual space available for 48 ports and uplinks is smaller because the product itself includes a bezel facing that includes graphics and other items comprising a user interface that is similar to previous products. 
   Previous uplink I/O devices, such as the GBIC (Gigabit Interface Converter) or the SFP (Small Form Factor Pluggable) module, have a relatively small form factor and sufficient space is available on the front face of the 1 RU switch for both the 48 ports and the dual uplinks. However, with the advent of 10 Gigabit Ethernet (10 GE) the uplink I/O device size has increased. 
   One type of 10 GE uplink I/O device is the MSA (Multi-Source Agreement) X2, which is defined in the X2 MSA specification which is hereby incorporated by reference. The X2 system utilizes a side rail support system which is mounted on a PCB (printed circuit board) with a connector disposed to receive the connector end of the X2 transceiver. The X2 transceiver is inserted into a switch and guided by the rail system so the X2 transceiver connector mates with the PCB connector. The module includes a bezel on the front which is used to hold a gasket for EMI protection. 
   Because of the increased size of the X2 10 GE I/O device it has not been possible to provide two 10 GE uplinks in a 48 port 1 RU switch. 
   BRIEF SUMMARY OF THE INVENTION 
   In one embodiment of the invention, two X2 modules are mounted “belly to belly” on opposite sides of a dual-sided PCB. The dual-sided PCB is mounted above the motherboard using vertical supports and is connected to the motherboard using a vertical connector. 
   In another embodiment of the invention, the dual-sided PCB has a thickness of about 0.2 inches to provide clearance between the front bezels of the X2 modules and provide structural support for the X2 modules. 
   In another embodiment of the invention, ribbon connectors are utilized to couple the X2 modules to the motherboard. 
   In another embodiment of the invention, the motherboard is cut out below the PCB module to provide extra space for ventilation. 
   In another embodiment of the invention, the modules have the same orientation and the upper module is mounted on the upper surface of an upper PCB which is connected to the motherboard using an interposer connector. 
   In another embodiment of the invention, the modules have opposite orientation with the upper module connected on the lower surface of an upper PCB which is connected to the motherboard using a interposer connector. 
   Other features and advantages of the invention will be apparent in view of the following detailed description and appended drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of an embodiment of the invention; 
       FIG. 2  is a detailed side-view of an embodiment of the invention; 
       FIG. 3  is a side view of an embodiment of the invention having a cut-away motherboard; 
       FIG. 4  is a side view of another embodiment of the invention; and 
       FIG. 5  is a side view of still another embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference will now be made in detail to various embodiments of the invention. Examples of these embodiments are illustrated in the accompanying drawings where like reference numerals denote the same or similar components. While the invention will be described in conjunction with these embodiments, it will be understood that it is not intended to limit the invention to any embodiment. On the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the various embodiments. However, the present invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present invention. 
     FIG. 1  is a perspective view of an embodiment of the invention. A 1 RU switch  20  has a front face having a first region  22  for holding 48 ports and a second region  24  for holding 2 MSA X2 10 GE uplink modules  26   a  and  b.  The front face also has space reserved for a user interface or console interface to be compatible with existing products. 
   The X2 modules  26   a  and  b  are mounted on a PCB board using rails  28 . In this embodiment the MidPak version of X2 defined in X2MS revision 1.0b dated 28 Feb. 2003 is utilized. The front of the module includes a bezel  26  and a receptacle  28  for receiving Tx and Rx connector plugs. The bezel abuts the front plate  22  of the switch. The X2 module includes fins for cooling. An MSA XENPAK 70 pin connector connects the electrical circuitry in the X2 module to the traces on the printed circuit board. 
   First and second X2 modules  26   a  and  26   b  are mounted “belly to belly” on a dual-sided PCB  32  which is connected to a motherboard  34  by a vertical connector  36  which connects traces on both sides of the dual-sided PCB  32  to traces on the motherboard  34 . 
     FIG. 2  is a side view of the embodiment depicted in  FIG. 1 . The dual-sided PCB  32  is positioned above the motherboard by spacers  40  and  42  connected to the chassis  43 . In this embodiment the thickness of the dual-sided PCB is about 0.200 inches to provide separation between the bezels  26  of the first and second X2 modules  26   a  and  b  and to provide mechanical support. In one embodiment, depicted in  FIG. 3 , the motherboard  34  is partially cut away below the modules so only three or four supports are available to support the dual-sided PCB  32 . 
   As depicted in  FIG. 3  the first X2 module  26   a  is connected to a first XENPAK connector  44  which connects circuitry in the first X2 module to the traces on the upper surface of the dual-sided PCB  32  and the second X2 module  26   b  is connected to a second XENPAK connector  46  which connects circuitry in the second X2 module to the traces on the lower surface of the dual-sided PCB  32 . 
   The space required by the  48  front mounted ports in the 1 RU switch requires that the dual 10 GE uplinks be stacked because there is not enough horizontal space in the front of the 1 RU switch, due to constraints such as the inclusion of a mode button, graphics, and other components forming a user interface similar to other products, to allow the modules to be disposed side-by-side. 
   In the “belly to belly” configuration depicted in  FIGS. 1 and 2 , the second X2  26   b  module is mounted upside down relative to the first X2 module  26   a.  A relatively thick PCB is required to support the second module stacked over the first. By mounting the X2 modules on the top and bottom sides of the dual-sided PCB  32  it is possible to stack the two modules in the small area  24  of the front face of the 1 RU switch that is not occupied by the 48 ports. 
   When using optical components sufficient cooling is critical to prevent signal degradation or loss of packets. The configuration depicted in  FIGS. 1 and 2  provides sufficient space to allow necessary air circulation to cool the components with the modules. 
   In an alternative embodiment, the first and second X2 modules  26  and  28  can be connected to the motherboard by ribbon connectors. 
   In a second embodiment of the invention, depicted in  FIG. 4 , the first X2 module  26   a  is mounted on the top surface of a one-sided PCB  60  and the second X2 module  26   b  is mounted on the motherboard  34 . A vertical connector  36  connects the one-sided PCB  60  to the motherboard. Alternatively, the first module  26   a  can be connected to the motherboard by a ribbon connector (not shown). 
   In a third embodiment, depicted in  FIG. 5 , the first module  26   a  is connected to the underside of a one-sided PCB  70  and the one-sided PCB is connected to the motherboard by either a vertical connector  36  or a ribbon connector (not shown). The second X2 module  26   b  is mounted on the motherboard  34 . 
   The invention has now been described with reference to the preferred embodiments. Alternatives and substitutions will now be apparent to persons of skill in the art. Accordingly, it is not intended to limit the invention except as provided by the appended claims.