We have found disable bits for 10GbE in NVM control word#3, but these bits only apply in LPLU mode as I understand it. We would like to limit the maximum link rate permanently so that it applies during PXE boot and normal operation without special settings.
Thank you for contacting Intel Embedded Community.
In order to be on the same page, could you please clarify if the design related to this situation has been developed by you or by a third-party manufacturer? In case that it is a third-party design, please give the model, part number , and where is stated its documentation.
Waiting for your answer.
Hello, @TMels :
Thanks for your clarification.
The information that may help you is stated in section 5.3.4, on page 178 of the Intel(R) Ethernet Controller X550 Family: Datasheet document # 333369. It can be found at:
Thanks for your reply.
There are registers that can be written to change the PHY configuration. These are in section 10 of the datasheet. As you noted, the available NVM configurations impact only the LPLU related settings.
To permanently disable 10 G operation would require the development of new PHY firmware (FW) that is not supported.
This PHY FW is autonomously loaded and is in full operation long before the MAC and SW can affect the auto-negotiation. For this reason, setting the registers from section 10 will require restarting auto-negotiation and would need to be reset after each reset that involves the PHY and any power cycling. This is likely ok for same session testing. I don’t see a solid path for the permanent setting of a lower link state. You could modify your driver say in Linux to only support 10G. This removes auto-negotiation. You will end up renegotiating link when the driver loads and any issues negotiating that link will end in no link which might not be a risk you want. The safer alternative, will be to change the auto-negotiation capabilities of the link partner to remove 10G as an option. Often the X550 is connected to a switch as a link partner. Switches will often have a great deal of configurability in their auto-negation options.
Could you please inform what speed you would default to? The question is about getting rid of 10G but this PHY also supports 5G and 2.5G. Are you looking to support those NBase-T speeds or maybe you were thinking 1G? If looking for 1G, you will also need to disable the 5G and 2.5G.
If you are looking for a 2.5G or 1G option, perhaps we can steer you to another of our products. Are you searching for a feature and a link speed or just the link speed?
We hope that helps, let us know if you can answer some of our questions regarding your use case.
Thank you for your thorough answer! We want to limit autonegotiation to start at 1G and go down from there. It sounds like the O/S and driver is our best option.
@Maecenas_INTEL: Thank you for the reply! My previous response was not complete. We would like to default auto-negotiation to start at 1G and go down from there. Based on your response we understand that we need to use the driver to limit the speed. We are already using several other Intel controllers for 1G speed, but in this case we are looking for ways to limit the speed in a build variant of our X550 product where a proprietary connector is used which is not 10G capable, so using a different controller is not really an option this time.
Thanks for your reply.
We had suggested you limit the link partner if you must.
You can renegotiate and limit the options in the driver. This will only work when the driver loads. It will try auto negotiate 10, 5 and 2.5 before getting to 1G. This would reset after the driver unloads or during some device resets.
By the way, we asked about your use case and if we could find them a 1G part but there is no answer from your side, could you please let us know the information related to this?