Accessing advanced BIOS features

[etaifour]

Hi - I'm running all the latest updates on Windows 11 24H2, including the AMI BIOS rev f.24.

All my drivers work perfectly. I've upgraded my machine to 64 GB of memory.

I've recently purchased an eGPU that connects via thunderbolt 4. The eGPU is non faulty (it was tried at the vendor's), but it doesn't run on my machine. It's a Gigabyte AORUS AI Box (an RTX 5090 32 GB).

When plugged in, the device is recognized by Windows as "DMC driver". I've reached out to the manufacturer who informed me that this indicates Thunderbolt handshake is failing. The remediation must happen at the BIOS level, by either changing the Thunderbolt security (from Kernel DMA to no security), or to enable 4G decode / MMIO if not already done. 

The BIOS seems to be hiding advanced settings.

I understand these settings are hidden to protect users from inadvertently causing malfunctions to their machines. Can someone from HP guide me how to access these advanced settings? Is this a paid service?

Please let me know - thank you.

[VikramTheGreat]

Hi @etaifour,

Welcome to the HP Support Community.
 

Thank you for posting your query. I will be glad to help you.

I understand what you’re trying to achieve with the Thunderbolt e-GPU setup; however, I’ll clarify this part clearly:

About BIOS advanced/hidden settings

On HP systems, advanced BIOS options (like Thunderbolt security levels, 4G decoding, MMIO settings, etc.) are intentionally locked/hidden.

These are not user-accessible and:

• Cannot be enabled through standard BIOS 
• Are not supported to be modified by HP support 
• There is no paid option or service to unlock these menus 

This is by design to ensure:

• System stability 
• Hardware compatibility 
• Thermal and power safety limits 

About e-GPU support

Not all HP systems support external GPUs over Thunderbolt, even if:

• Thunderbolt 4 port is present 
• The device is detected at the OS level 

Support depends on:

• Motherboard design 
• BIOS-level Thunderbolt implementation 
• Power and PCIe lane allocation 

If the system is identifying it as “DMC driver”, that typically indicates the Thunderbolt controller is not completing proper PCIe tunnelling/handshake, which aligns with what the vendor mentioned, but this is controlled at the firmware level.

Important limitation

HP does not support modifying Thunderbolt security from Kernel DMA to No Security, or enabling:

• 4G Decoding 
• MMIO expansion 

on consumer/commercial systems where those options are not exposed.

To check compatibility

If you can share:

• The exact HP system model (full product name) 

I can help confirm whether:

• E-GPU is supported on that platform 
• Or if this limitation is expected for your device

I hope this helps.

Take care and have an amazing day!

[etaifour]

Thank you for your reply, VikramTheGreat,

The exact model is HP ENVY 34 inch All-in-One Desktop PC 34-c1000 (4G584AV).

The model of the eGPU is AORUS RTX 5090 AI BOX (Spec sheet: https://www.gigabyte.com/Graphics-Card/GV-N5090IXEB-32GD)

The eGPU manufacturer state on their page that it runs on Thunderbolt 5.0, but in a support message has acknowledged that it works on Thunderbolt 4. I've returned the eGPU to the retailer for assessment: they have tried it on a Thunderbolt 4 machine and it ran successfully. I'm happy to share these messages on a private channel with HP if they are helpful.

This leads to an incompatibility caused by the locked down configuration of the BIOS of my machine.

None of the technical specification sheets of my HP Envy All-In-One mention that Thunderbolt 4.0 is preconfigured in a specific way that prevents some devices to run, for a reason or another. Neither could I find any article on HP's documentation asking to reach out for support to validate whether an external device will run or not.

This means that unless HP can help unlock the BIOS to expose all the Thunderbolt configuration parameters (mainly MMIO and 4G encoding in my case), HP is in breach of contract as it would be false advertising a product, claiming it supports Thunderbolt, while in reality it supports "some" thunderbolt, failing to mention this exclusion anywhere in its presales documentation.

I hope you can provide a resolution to this matter, either in the form of a way to access these BIOS settings - I acknowledge that modifications to the system could render the system unusable which I will be accountable and responsible for, including to any damage to the system, and HP will not be liable in any way, or by pointing to any presales documents on your site that indicates how some BIOS settings are locked down. I might have overlooked this detail when I purchased the machine, and I appreciate your help.

Thank you,

Regards,

[VikramTheGreat]

Hi @etaifour,

Thank you for taking the time to explain the situation in such detail. I can see you’ve done a thorough job testing the eGPU and narrowing down where the limitation may be. I understand why this would be frustrating, especially when everything appears compatible on paper.
 

That said, I want to be transparent with you. On systems like the HP ENVY 34-inch All-in-One Desktop PC 34-c1000, the BIOS is intentionally configured and restricted by design. These settings are validated by HP to ensure system stability, thermal balance, and hardware reliability. Because of this, advanced options such as Thunderbolt MMIO allocation or Above 4G Decoding are not exposed for manual changes, and we’re not able to unlock or modify them.
 

Additionally, external GPU configurations, especially via Thunderbolt (like with your AORUS RTX 5090 AI BOX), fall outside of HP’s supported hardware configurations for this model. While Thunderbolt 4 is supported for certified devices, compatibility with all third-party high-performance peripherals (particularly eGPUs) isn’t guaranteed, and we don’t have the ability to validate or enable unsupported configurations at the BIOS level.
 

For the best possible path forward, I would recommend:

• Reaching out to an HP Authorized Service Center or Store 
• Or consulting with a qualified IT professional / system integrator 

They can physically assess the setup and may suggest alternative configurations or compatible solutions that work within the system’s design limits.
 

I do understand this may not be the resolution you were hoping for, but I want to make sure you have clear and accurate guidance. If you need help locating an authorized HP center near you.

To contact HP Authorized Stores, click here:  HP® Service Center Locator - United States | HP® Support.

Please feel free to contact us here anytime you need any further assistance.

Have a great day!