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The Intel® Server Board S5520HC supports the Intel® Xeon® Processor X5670
The board is not included as compatible with the processor because this board was sold included with the Intel® Server System SC5650HCBRPR.
Both boards are very similar, the S5520HC includes more numbers of PCIe lanes, this board is considered as Server board while the S5520SC as Workstation.
It is possible to compare both boards on the link below: Compare Intel® Products
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