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Precision 7720 deactivates AMD 7100 GPU when system starts


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I bought a cheap version of a Dell Precision 7720 and upgraded it with a XEON Mainboard and an AMD Fire Pro WX7100. When I do a BIOS-Reset (CMOS), the screen stays black and the system reboots three times (I think, this is normal). Then the screen is on and I can enter the BIOS. The dGPU is listed correctly but - no matter what I do (I tried disabling TPM etc) - after leaving the BIOS, the System restarts twice and then the GPU is deactivated. Not shown in BIOS, not visible via lspci-command.


I tried to update the BIOS, with no effect. I have no chance to update the VBIOS, because the GPU gets deactivated before any boot procedure. My older FirePro M6100 works, but not all display ports can be driven. Ok, this GPU was never meant to be used with this laptop.

Does anyone here has an Idea, what I could try else? I expect the dell support to be not very helpful... Which is finally one reason why I didn't buy a new 4000€ Precision 7740 xD

Maybe - is it possible, that no GPU can work, that has more Memory, than the system itself?

Edited by MitjaStachowiak
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Well, I bought a AMD 7100X for HP servers. I've used the old mainboard of my Dell 7720 on a docking station with external screen and keyboard, to quickly test the GPU and it here worked fine. In the BIOS, the dGPU is activated and listed as unknown GPU. Then I opened my Laptop, took the Heatpipe and installed it onto the docked mainboard, put in my NVME, boot and the GPU still worked fine. In the operating system, lspci gives me

VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Tonga XT GL [FirePro S7150] (rev 01)

The chip on this card is larger than on the original 7100, I bought on ebay (used and not working, maybe defective). So the 7150 is newer and larger. Well, I played Metro Exodus for a while, so far it is possible with external keyboard and touchpad^^, but the graphic was very nice.


Then I put the GPU into my Laptop with the new XEON-MB, but here, it isn't detected by the BIOS. After the CMOS-Reset, just the Intel-Graphics is active :-/


Do you think, that the XEON-CPU is the reason, why the GPU doesn't work? I don't. Its more likely that one of the latest BIOS-Updates, installed during this year, deactivates this GPU or maybe any unknown GPU...

Maybe I should think about BIOS-downgrade, if possible. I found a store, that is able to order an original AMD 7100 from Dell, but they want 1500€!!! Moon price!


If anyone here is interested in doing a DELL Precision BIOS-Mod to fix this issue, I will send my MB, Docking-Station and AMD 7150 to him or her ;-)
Otherwise I will try BIOS-Downgrade. Or alternatively: Does anyone know, which IC is the BIOS on a Dell Precision 7720 MB? Then I could maybe solder the IC from the old MB...

Edited by MitjaStachowiak
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Okay, it seems, it wasn't the BIOS-Version, that caused the problem but the wrong heatsink. I used the Nvidia MXM-type A heatsink from previous graphics, emeried some cooper where the GPU is located an added some other cooper plates where the voltage converters are. What I didn't realized is, that some screws from the keyboard grounding go through this heatsink and hit my additional cooper plates. So when I installed all the other things of the laptop, this screws bent the heatpipe and the GPU's PCP and somehow caused that the GPU then was not longer detected. I think, I did some little damage to the GPU this way - but when I now leave out the screws from the keyboard grounding and don't tighten the heatsink's screws too much, it works.


I cannot see the GPU-temp, because there is no GPU temperature sensor active on Dell 7720. It wasn't even active for original Nvidia GPU. I think, they just measure the CPU temp and because it's the same heatpipe, that connects CPU, GPU and fans, the fan speed is ~correctly controlled this way...


This Server-GPU seems to have no display outputs. On the Precision 7720, the Intel Graphics can drive nearly all display connectors, if configured in the BIOS. But there is no active Intel HDMI audio then. So I cannot use digital audio output :-/


Maybe if someone could integrate the display configuration of the AMD 7100 Dell-VBIOS into the 7100X/7150 VBIOS, we could get this GPU fully compatible.

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