Firmware, expansion roms, and driver for Connectx-4 Lx on system with UEFI BIOS.


I’ve been working on getting Connectx-4 Lx (MCX4421A-ACQN) to work with a non-legacy bios and have been running into a few issues during the process. I have the following questions:

  • What is the correct drivers/firmware to use for this process if I want to embed the driver into my BIOS’ source code? I’m currently using the 14_22_14_RELEASE.efi file.

  • Your product’s documentation mentions that the preboot option EXP_ROM_UEFI_x86_ENABLE needs to be enabled for the card to show up in as a boot option. I know this is the case when using the expansion rom method (i.e. burning .efirom file using flint), but is this also the case when using the 14_22_14_RELEASE.efi file?

  • Similarly, I have only been able to get HII information to appear in bios menu when I enable the preboot option UEFI_HIIEN in mlxconfig. Is there a driver that I can embed into the bios that already has UEFI_HIIEN and EXP_ROM_UEFI_x86_ENABLE enabled? Or is there a method to make a .efi file with these preboot settings enabled?

  • Is there a document that explains in detail what all your preboot options do for the Connectx4 Lx?



Hi Stephen,

According to our records your account has a valid support contract with us , i suggest to open a support ticket at

We will be happy to assist and provide you with the best support.