Question Optiplex 7040 not detecting discrete GPU

[Jobble_Gobble]

Kia Ora, Hello,

I have recently purchased a Dell Optiplex 7040 and I want to add a discrete GPU. I consider myself to be very much a beginner when it comes to this stuff but I have attempted a great number of things and cannot get the system to even register a PCIe device. I have tried basic troubleshooting such as removing the CMOS battery, updating the BIOS, enabling legacy boot mode, and following the steps provided in this article.

I have also tried swapping the slot the card uses as well as installing a network card in all of the slots to verify they work. Low and behold the network card is detected fine and drivers are automatically installed on boot. As soon as I change that to a discrete GPU the system no longer displays any device in the used PCIe slot. This is in both device manager and in BIOS.

As far as I can tell in my limited capacity the BIOS or maybe the Win10 install has some setting that doesn't check for a GPU or something. I should also mention as it may pertain to this matter. The GPU is driven by an external power supply separate of the proprietary one supplied with the PC as that didn't have any 6 pins. This PSU is 500W and exclusively runs the GPU. I wasn't sure if this was the cause of the issue but the gentleman who sold me the PSU and GPU assured me it wasn't.

The system specs are as follows:

i5 6500

Win10 Pro

16gb Gskill Ripjaws DDR4

Radeon HD 5770

BIOS v1.8.1



Any help on this matter would be immensely appreciated.



Nga Mihi, Regards,

Jacob

 

[thestryker]

Is the fan on the GPU spinning when it's plugged in and the system is turned on? If not then it's not getting enough power to turn on which could be the issue.

 

[Misgar]

Unplug the 5770.
Connect a monitor to the motherboard graphics port (iGPU).
Start the computer and enter the BIOS.
Look for an option to change the internal/external GPU boot order.

If the BIOS is configured to use the internal port first (iGPU), you won't see anything on the monitor when it's connected to the external card (5770). The graphics output will still be directed to the iGPU port on the motherboard.

Change the BIOS to "PCIe card first" (or similar) instead of "iGPU first" or "Internal GPU".
Save the BIOS setting and shut down the PC.
Disconnect from mains.
Plug in 5770.
Connect monitor to 5770.
Switch on and keep fingers crossed.

Good luck running the 5770 from two power supplies at the same time. It will draw up to 75W from the PCIe slot (computer PSU) and the remainder from the external 500W PSU (6/8-pin connectors).

Are you switching on both PSUs simultaneously? It's a bit of a Heath Robinson bodge and hardly ideal, but it should work if you get the timing right.

A much better solution would have been to upgrade the Optiplex 7040's PSU, but that might be difficult if it's a small form factor case.

If there is room in the Optiplex case for a standard ATX PSU, I'm surprised the gentleman who sold you the graphics upgrade didn't suggest running everything from a single upgraded PSU.

 

[Jobble_Gobble]

I really appreciate the responses so far thank you! The fans on the GPU are spinning up on boot but I have also confirmed that happens without the 6-pin connected so I'm not sure it means much, for what it's worth the fan on the second PSU does not spin which may mean something.

The setup is 110% a bodge, I failed to mention in the post that the gentleman who sold me all the parts was from a computer recycler and I am a very indebted student so I have few funds to work with and live in a country with a very small second-hand market. I have gone into the BIOS to manually adjust the PCIe order but I am only presented with two options "iGPU" or "Auto", I have selected Auto.

I'm not too sure about switching the PSUs on simultaneously, I just plug both power cords in, flip the switch and turn on the PC, sorry I'm not super familiar with all this.

Ideally I would just rip the RAM and CPU out of the system and dispose of all Dell's proprietary garbage but unfortunately financial constraints are preventing that right now.

 

[Misgar]

If the GPU card has any 6/8-pin connectors, they must all be connected to a PSU, otherwise the card may refuse to start up.

Auto should allow the system to work with the monitor connected to any graphics port. The BIOS should detect the port connected to an active monitor and route video accordingly.

If the mains switch you refer to is for a power strip with the two PSUs attached, they'll both come on at the same time which is good.

Some ATX power supplies do not switch on the internal fan, until they supply several hundred Watts. If the load is not excessive, the fan may never switch on.

 

[thestryker]

Is the secondary PSU just another regular ATX power supply? If so you need to do something regarding the power on as they don't just start providing power because you flipped a switch.

 

[Jobble_Gobble]

Is the secondary PSU just another regular ATX power supply? If so you need to do something regarding the power on as they don't just start providing power because you flipped a switch.

Thanks so much for the response! The power supply is regular ATX but does date back to 2007. I did wonder how it would just know to turn on so that seems very possible. Is there any chance you could point me in the direction of what specifically I need to do?

 

[thestryker]

Thanks so much for the response! The power supply is regular ATX but does date back to 2007. I did wonder how it would just know to turn on so that seems very possible. Is there any chance you could point me in the direction of what specifically I need to do?

TechPowerUp

www.techpowerup.com

That's the basics of it, but there are probably other ways to go about it.

 

[Jobble_Gobble]

TechPowerUp

www.techpowerup.com

That's the basics of it, but there are probably other ways to go about it.

Absolute legend, thank you so much. I will attempt that shortly.

 

[Jobble_Gobble]

TechPowerUp

www.techpowerup.com

That's the basics of it, but there are probably other ways to go about it.

This solved the problem, thank you so very much I have spent days tryna solve this. I wish nothing but the best for you my friend.

 

[thestryker]

glad to hear it worked out