HP EliteDesk 705 G4 will not start up after replacing graphics AMD Radeon RX6400

[Fibonacci82]

Hello everyone, I just purchased a HP EliteDesk 705 G4  with a Ryzen 7 2700 and I was attempting to add a Radeon RX 6400 graphics card. If I put back the graphics card that came with the computer, it runs fine.I have two other G4’s with Rzyen 5 3400 and they accept the Radeon RX 6400 with no issues. I have tried enabling and disabling the legacy boot and have disabled, the securilock in BIOs. The PC will run for a few seconds, all the fans are spinning, and then it will shut off and restart, and it will continue to do that until I turn it off. Any help would be appreciated

[Bill_To]

Greetings @Fibonacci82 

That is strange. The 6400 runs fine in two different, identical G4 PCs.

Have you tried setting BIOS to defaults using the factory GPU. 

Shut down the PC.

Install the 6400 to see how it goes.

Or do a CMOS reset.

The 6400 works in other G4 PCs and the problematic G4 PC can do discrete graphics using the HP factory graphics card.

The 6400 runs off the PCIe slot so it does not appear to be a power supply problem.

This problem is really weird.

Are all G4 PCs using the latest BIOS version?

Regards

[Fibonacci82]

Thank you for the quick reply, I tried all your suggested steps and I’m getting the same results. This motherboard seems to be slightly different than my other G4’s. it does not have a functioning integrated graphics card on the motherboard. This is the second computer with the same motherboard that I’ve purchased because I bricked the first one by disabling the PCIE slot and with no integrated graphics card I just get six beeps which indicates a problem with the graphics card. With no display, I have no access to bios. I also tried to replace the motherboard only, but could not find any online. The motherboard part number is L35845-001.

[Bill_To]

Greetings @Fibonacci82 

My pleasure.

I don't know what is happening with one of your G4 PCs??

I have had problems with retail MBs after installing a different discrete graphics card when Secure Boot is enabled.

I had to use the CSM BIOS setting. This would be Secure Boot disabled, Legacy support enabled on a HP MB.

But newer BIOS updates installed on the problem retail MBs fixed the problem; the new graphics card would work using Secure Boot.

It seems to be a component (graphics card) Secure Boot Key problem when Secure Boot is enabled.

I had to use a Secure Boot custom keys setting in the BIOS to get the PC to boot using a new graphics card.

I don't know if you can do this on the G4 PC.

PCs are complex beasts. Secure Boot and TPM add more complexity.

Maybe someone in the HP Business Forum can assist.

Regards

[Fibonacci82]

Thank you, I’ll try the other forms.

[DragonStar9]

I've run into the same problem. Form what I can surmise, the 705 G4 bios doesn't seem able to recognize the RX 6400 to pass post. That's based on the fact that I can use the 6400 with a 2400g which has an iGPU that it can use to post with and load into Windows or bios. With the pro 2700 it just keeps cycling on and off and that's with trying bios setting and testing on two different 705 G4 that are Ryzen 2000 models.

If that's the case, short of having a modded bios that can bypass that step or that has proper/newer uefi protocol, I don't think it can work.