Case Studies

Cavium Thunder x Based Server Board

Design, testing and productization of a dual CPU based  backplane server board based on CN88XX processor.

Results / Outcomes

System Design and Implementation Details

SL Category

Description

1 Interfaces availed 

DDR4 RDIMM, 1x QSFP+(40G), 2x SFP+(10G), 1x USB 3.0, 1 x USB1.1,

  • 1x 10/100/1000 LAN, 1x DB9, 1x VGA, 
  • 1x X8 PCIe connector on board,
  • 1x X24 connector with X8 electrical connection. 
  • 2X 0.5mm pitch 50 pin back plane connector
2 Design Challenges
  • Productization of dual chipset server board with a board management controller with ARM 64 powered CPU and 288-pin RDIMM connector
  • Power design involving high current rated programmable buck regulators which source current up to 128A
3 Hardware Design (Schematics)
  • Complex power section design in adhering to PCIe electro-mechanical spec.
  • Part selection to minimal foot print as possible to accumulate all interfaces in required PCB dimensions.
  • Active heat sink and TIM material selection.
4 PCB Design (Layout)
 
  • Half height/Half length PCIe card (167x 65mm), 12 layer 1.6mm thick PCB.  
  • Routing complexity involving differential pair and group length matching and intra spacing for the  PCIe 2.1 Interfaces between Octeon/Nitrox/ Intel chipsets placed on single side of PCB  
  • Very high current sourcing power plane cutting for various voltages on board. 
  • Highly challenge to achieve all above specification in required form-factor. 
5 Fab and Assembly House co-ordination
  • DFM and DFA reviews 
  • Low cost CBOM’s with low cost alternates identified for high cost parts, life time check for critical components in design including NAND and NOR flashes
  • Manufacturing support with alternates identified for components going to EOL/obsolesce
6 Board bring-up and Testing
  • Initial bring-up of the board followed by detailed Electrical interface validation(EVT) including  interface validation of XAUI, PCIe interfaces
  • ispPAC(voltage/reset sequencer) programming for power/reset sequencing
7 Firmware Application Development
  • Development of bootloaders for Octeon chipset including memory configuration of NOR flash and NAND flash, boot configuration strapping, PCIe configuration etc
  • Development of manufacturing test scripts for board testing.
  • Development of PCIe/XAUI drivers for chipsets
8 Mechanical and 3-D Design
  • Prepared the 3-D model of the board.
  • Worked with 3rd party mechanical team for developing heat sink and  I/O bezel 

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