I need some help understanding the interaction between CSM, Secure Boot and a custom vBIOS.


I have an ASUS N550JK laptop with a NVIDIA GTX 850M graphics card. NVIDIA has the card locked down so that you only overclock up to about ~1200 MHz on the core, so I modded the vBIOS to overclock the card further. Now the vBIOS lives as a module in the mainboard BIOS. The overclock works fine when I boot up with CSM (Compatibility Support Module) Enabled, and Secure Boot off, but will not work with CSM Disabled, or Secure Boot on, which will boot with stock clocks. This happens on both Windows 10 and Windows 8.1 (both UEFI installs).


Does anyone know why this is happening or if there's a way to allow me perform a secure boot, but still retain my vBIOS overclock?

Here's a link to my BIOS: http://1drv.ms/1ML8e8i

TL;DR: Disabling CSM disables my vBIOS overclock. Why is this?

Fantastic. Thanks getting back to me so quickly! I figured it would be something like that.

If that's the case, then how does the GPU get initialized? Is there a separate EFI module for the GPU that I can modify so I can continue using Secure Boot?

Zitat von Fernando im Beitrag #4

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Zitat von tocirahl im Beitrag #3

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If that's the case, then how does the GPU get initialized? Is there a separate EFI module for the GPU that I can modify so I can continue using Secure Boot?

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The GPU is initialized by a special GopDriver, but I am rather unsure, that you will be able to do the desired modification with this EFI module.

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Zitat von Fernando im Beitrag #4

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Zitat von tocirahl im Beitrag #3

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If that's the case, then how does the GPU get initialized? Is there a separate EFI module for the GPU that I can modify so I can continue using Secure Boot?

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The GPU is initialized by a special GopDriver, but I am rather unsure, that you will be able to do the desired modification with this EFI module.

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Zitat von Fernando im Beitrag #7

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Zitat von tocirahl im Beitrag #6

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Any idea how to extract the NVIDIA GOP module using MMTool?

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What is the problem? Just hit the "Extract" tab, highlite the module, choose the "extract uncompressed" option, click onto the "Extract" button and give the extracted file a name as *.ffs file.

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Zitat von Fernando im Beitrag #9

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Zitat von tocirahl im Beitrag #8

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I'm having trouble figuring out which module corresponds to the NVIDIA GOP.

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If you have a discrete NVIDIA card inserted into a PCIe slot, you will not find any NVIDIA GopDriver within the mainboard BIOS. So you have to open the BIOS of the graphics card.

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Fernando is right about the VBIOS not getting loaded when CSM is disabled. But there is no EFI for your Nvidia card, so the VBIOS is loaded instead. Your system is using Optimus most likely, so the Nvidia card is not connected to the screen, therefore no EFI is needed during boot, all is done by Intel GOP driver. How is then possible to have your results? Simple, there is a second VBIOS in C5D7EAAD-B218-482C-A909-E3B8CDB00E94, which I assume is identical to the first one, but is loaded during EFI boot:



There is the possibility to add an Nvidia EFI driver to your card.

This is exactly what I was looking for. Thank you so much!

Zitat von lordkag im Beitrag #11

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@RypeDub

It is something I wrote to help in such cases. It can be found here. Just run it on your desired VBIOS file and if you think you might flash your card with an updated GOP, post there the original file and the hash of modded file, so I can double check the result.

There is something about your laptop. When you check the content of the EFI Firmware, you should see that there are multiple versions of Nvidia VBIOS. I think some of them are duplicates, given the same ID, but can't be sure, as they have a different sign-on message. At least the last two from CSMCORE are duplicates, as they are hidden, not accessible with MMTool. They too have a slightly different sign-on message, but given the same ID and a version bump, I should say it shouldn't be a problem in removing them. Check with GPU-Z what version you have and keep that one.



If you want a GOP update, take the one(s) from the C5D7EAAD-... GUIDs and run them through GOPupd. You will see they have an old GOP.