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DS80PCI810: Length question

AJ Cheng
Genius 3615 points
Part Number: DS80PCI810


Hello.

We want to know, suppose that there is 16 inch from the CPU side to the slot, and the preset can be pass. If the trace design needs to double and re-driver is not use, the Preset maybe will fail, but after use the re-driver, Is the re-driver is bypass mode in the preset? If so, is it not necessary to add a re-driver? Or is the re-driver in the performance are good of the preset, there will also be an amplification effect of the enhancement? Thanks.

  • 0
    TI__Mastermind 43795 points

    Hi AJ,

    The PCIe preset testing is done with very low speed data to minimize or even eliminate loss across the distance to the slot.  So a 16 inch channel or even a 32 inch channel is likely to pass Transmit Preset testing without any issues.  However, just passing Transmit Preset testing is not a guarantee that the PCIe link will work.  The maximum channel attenuation for PCIe links in Gen3 is ~ 22dB.  This will be difficult or impossible to achieve with a 32 inch distance to the slot.

    Because the DS80PCI810 uses a linear drive and CTLE equalization to recover high frequency attenuation, the low frequency portion of the waveform is only minimally altered.  By retaining the low frequency waveform characteristics, the Transmit Preset testing can be completed even with this redriver in the channel.

    Regards,

    Lee