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DS80PCI102: DS80PCI102 PCIe gen2 and gen3 SI OK but found PCIe gen3 Preset test failed

Eric Li3
Prodigy 150 points
Part Number: DS80PCI102

Hi Madam/Sir,

In our Intel Core i main board, there has a DS80PCI102 to re-drive the PCIe gen 1/2/3 signal pairs, see below for schematics.

It passed PCIe gen2/3 SI measurement but failed at PCIe gen3 Pretest, see below for Preset result.

How can we resolve this issue? please kindly share us your comment or thought.

Thanks a lot!

  • 0
    TI__Guru* 93670 points

    Hi Eric,

    I am assuming source by itself meets PCIe Gen3 requirements. Reviewed your schematic and here are a couple of recommendations:

    1). Pleased tie RATE_2 to GND through 20K ohm. This will enable PCIe Gen3 without de-emphasis.

    2). Then you can start with the lowest EQ settings and increase one step at a time - if needed - to pass Gen3 presets.

    Regards, Nasser

  • 0 in reply to Nasser Mohammadi
    Prodigy 150 points

    Hi Nasser,

    Thanks for your support.

    We tried to disable De-emphasis and increase the EQ settings but the PCIe gen3 Preset seems failed still.

    please kindly share us your comment or thought.

    furthermore, for Table 2., Equalizer Settings, there is a note (1) The suggested equalizer CTLE settings are based on 0 dB of TX preshoot/de-emphasis. In PCIe Gen 3 applications which use TX preshoot/de-emphasis, the CTLE should be set to a lower boost setting to optimize the RX eye opening.

    what does it mean?

    Regards,

    Eric Li

    item no.2

    item no.3

    item no.4

    item no.5

  • 0 in reply to Eric Li3
    TI__Guru* 93670 points

    Hi Eric,

    PCIe protocol provides different de-emphasis levels for signal conditioning. These are called presets and range from P0 through P10. P4 does not have any pre-emphasis or TX signal conditioning. Note in the data sheet specifies that P4 - no signal conditioning is used. 

    Please run the same test using the following settings:

    1). Please make sure RATE_2 pin is tied to GND through 20K Ohm R.

    2). Use EQ 0 and without de-emphasis.

    I did not see these settings in the table above.

    Regards, Nasser

  • 0 in reply to Nasser Mohammadi
    Prodigy 150 points

    Hi Nasser,

    Thanks for your support.

    Here is the PCIe gen 3 Preset result using the following settings:

    1). RATE_2 pin is tied to GND through 20K Ohm R.

    2). Use EQ 0 and without de-emphasis.

    please kindly share us your comment or thought.

    Regards,

    Eric Li

  • 0 in reply to Eric Li3
    TI__Guru* 93670 points

    Hi Eric,

    Please use a certified lab such as iPass in Taipei to check TX compliance. There is a certain test setup that needs to be used to check TX compliance.

    Regards, Nasser

  • 0 in reply to Nasser Mohammadi
    Prodigy 150 points

    Hi Nasser,

    Thanks for your comment.

    We thought it might not relate to certified lab since our SI team have good knowledge and skill on checking TX compliance.

    If there has any possible way to improve it, please kindly share us.

    Regards,

    Eric Li

  • 0 in reply to Eric Li3
    TI__Mastermind 18850 points

    Hi Eric,

    Nasser is out of the office but should be back next week. Can you tell us more details about your TX compliance setup from a hardware level? What test equipment, endpoints, etc. are being used and how are they connected?

    Best,

    Evan Su