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This is interesting because, sfp+ offers an inexpensive way to use optics to connect two PCIe x1 devices. But I do not know enough about sfp+ to know if I can simply connect up pcie lanes on a motherboard to a sfp+ transceiver card.

I understand that I shall not have sideband signal access. But I can live with that as I do not need to power the device via PCIe.

Thank you. Best regards,

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Yes, you can do this -- I've done it up to Gen2 speeds.

However, we used PCIe packet switch ICs from PLX on both sides of the PCIe link. This is because these parts let you tweak via registers the exact link training behavior, in addition to signal parameters like emphasis / de-emphasis, boosting signal strength, etc.

They might have an app note on this now, not sure. The Gen2 parts no longer require a NDA, so you could pull up the data book for the 8604 or similar.

You could potentially build a simple x1 add-in card with a PEX8604 on board, one lane connected to the motherboard slot, and two off to SFP lanes.

The other side / target device would want the same chip on the other end. You could flexibly connect various ports on the 8604 based on strap options you toggle with DIP switches.

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  • \$\begingroup\$ Krunal, how do you handle the prstn#? \$\endgroup\$ – shparekh Apr 23 '16 at 6:10
  • \$\begingroup\$ I actually don't remember -- I don't think we used it, honestly. That's more useful IMHO for feeding simple circuits on a board, like turning on a power switch or LED or setting some kind of I2C slave address. To detect presence, you can use the hot plug registers like SLTSTA or similar that has presence bits when a link comes up. \$\endgroup\$ – Krunal Desai Apr 25 '16 at 21:58

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