System won't post with GPU installed

[884248]

Hello!

 

I am working on my first build, and when I install the GPU the system won't start. Here are the parts:

 

Mobo: B760I Aorus Pro [newegg link]

CPU: Intel i7-14700K [newegg link]

PSU: Corsair SF750 80+ Platinum [newegg link]

Memory: Corsair Vengance 64Gb (2x32) DDR5 6400 [newegg link]

Cooler: DeepCool LT720 360mm AIO [amazon link]

GPU: MSI Ventus 3X 4080 Super [best buy link]

 

When I don't plug in the GPU, and connect my monitor to the mobo HDMI output, everything works fine on integrated graphics. I've been able to download and flash the most recent bios version this way, but that doesn't help the issue. When I plug in the GPU and hit the power button, I hear a click in the PSU (like normal) but no fans (AIO and PSU fans) spin up at all. No LEDs come on on the motherboard. I'm not positive, but I think this motherboard doesn't have debugging/status LEDs?

 

Thing's I've tried:

* most recent bios (F8, link)

* Plugging in the GPU to the PCIe slot, but plugging the monitor into integrated graphics. That doesn't work either (same symptoms).

* Unplugging the GPU from the motherboard and the power connectors, but leaving the GPU power connectors plugged into the PSU, same results.

* Switching which 8-pin modular ports I'm using on the PSU for CPU vs GPU, same results.

* Changing PCIe slot protocol from 'auto' to 'PCIe gen 4',m same results.

* Wiggling the GPU end of the PSU cables while trying to boot it, allegedly some of the 4080 supers have shoddy connections on the GPU side?

 

I'm kind of at a loss, but it seems strange to me that the system won't boot with the GPU cables plugged in but no GPU plugged into the other end. Is that normal? It also seems strange that absolutely nothing happens when I power on the system -- no fans or anything.

 

Unfortunately this is my first build so I don't have other parts or another system to plug this stuff into to test it.

 

Things I could try next:

 

1) Get a motherboard speaker? I wasn't able to find any status LEDs on this motherboard, and the manual didn't mention it so I'm not sure how else I could debug this other than listening to the tones?

2) Install Windows, etc... using integrated graphics and then try setting up the GPU?

3) Getting a new GPU to 3x8 pin PSU splitter cable? Allegedly those are bad sometimes?

4) My PSU came with 2 8 pin to 8 pin cables and 3 8 pin to daisy-chained 6+2 pin cables. I'm currently using one of the 8 to 8s for my CPU, and the other 8 to 8 for my GPU along with two of the 8 to 6+2 cables. The 6+2s are daisy chainable (they look like this), but I'm not daisy chaining them. Instead, I'm using the plugs nearest to the PSU end of the cable. Is that right?

3) <Your idea here>

4) Take the GPU to a shop to see if it works or not.

5) RMA GPU.

 

Any ideas? I've attached a picture of my bios.

 

 

[goatedpenguin]

I don't think a 750W psu is sufficent to keep that whole pc powered hence, it can function without the gpu power draw. Not to mention your power draw on pccpart picker is 680W while your using a 750W sf PSU. 

[884248]

Interesting, I had read that other people were ok with a similar setup to mine, and PC part picker said it was "ok" so I pulled the trigger and bought the PSU. Perhaps I just needed more headroom? How much headroom does one normally need? Kind of a bummer...

[goatedpenguin]

12 minutes ago, 884248 said:

Interesting, I had read that other people were ok with a similar setup to mine, and PC part picker said it was "ok" so I pulled the trigger and bought the PSU. Perhaps I just needed more headroom? How much headroom does one normally need? Kind of a bummer...

idk if the pcpartpicker shows the min power draw or max draw cuz that to me is probably minimum power draw and you might be drawing more power than that, perhaps use a 850w psu?

[IkeaGnome]

37 minutes ago, 884248 said:

My PSU came with 2 8 pin to 8 pin cables and 3 8 pin to daisy-chained 6+2 pin cables. I'm currently using one of the 8 to 8s for my CPU, and the other 8 to 8 for my GPU along with two of the 8 to 6+2 cables. The 6+2s are daisy chainable (they look like this), but I'm not daisy chaining them. Instead, I'm using the plugs nearest to the PSU end of the cable. Is that right?

I'm curious about this. The 4080 Super Ventus should have the 12 pin PCIE 3.0 connector on the graphics card, not 8 pin connectors. 

 

I also can't tell if it's your picture or the monitor, but there's a lot of artifacting on the bios main page. 

 

I would probably start with taking the CPU back out and checking your socket pins.

9 minutes ago, goatedpenguin said:

idk if the pcpartpicker shows the min power draw or max draw cuz that to me is probably minimum power draw and you might be drawing more power than that, perhaps use a 850w psu?

That's fine that that's "to you". That's not going to keep the computer from posting. 

The graphics card doesn't have a check built in to look for the size of the powersupply and then just keep the power supply from not turning on.

A lower wattage power supply will just crash under load. 

14700k tops out at 181W with a good overclock and the 4080 super tops out at 402W. I don't know why you'd need 300W of headroom just to post. 

Feel free to prove me wrong though.

 

Edit: 

37 minutes ago, 884248 said:

4) My PSU came with 2 8 pin to 8 pin cables and 3 8 pin to daisy-chained 6+2 pin cables. I'm currently using one of the 8 to 8s for my CPU, and the other 8 to 8 for my GPU along with two of the 8 to 6+2 cables. The 6+2s are daisy chainable (they look like this), but I'm not daisy chaining them. Instead, I'm using the plugs nearest to the PSU end of the cable. Is that right?

I would make sure you're using the correct cables.. Your power supply comes with 2 cables for the CPU, and 2 cables for the graphics card. 

Spoiler

Graphics card ONLY uses the ones labeled PCI-E. You're going to have to daisy chain one and that's fine. 

 

[884248]

Interesting! I'm away from my build area right now, but I'm almost positive I'm using one of the CPU PSU cables for the GPU connections. The GPU came with this PSU cable:

 

 

And a little piece of paper that said I should plug in separate PSU cables to each of the 3 branches -- no daisy chaining. So I should use the three 6+2 PCIe cables for the GPU and not use the extra CPU one?

[QuantumSingularity]

This is the cable content for your PSU:

 

 

Idk what logic they followed putting 2x 4+4 CPU cables and only 2x 6+2 PCIe, but you will have to use the second connector on one of the 2 PCIe cables (circled them in red) and plug it into the 3rd connector of the adapter. That GPU doesn't boot unless all 3 of the connectors of the adapter are occupied. 

As if the PSU would hold under load - it's right on the limit. The minimum required by MSI in the documentation is 750W so when it starts, the first thing you should do i run a stress test. That GPU peaks at ~360W and with 14700k hitting almost 300W (299,5 is the highest i've personally seen during stress testing), you might be tripping some protection.

[884248]

You're right--that is bizarre! You're sure I don't need to get another 6+2 PCIe cable and that daisy-chaining is fine? Don't want to fry my GPU... Also, why do they even allow the 4+4 cable to even fit into the GPU ports?

[QuantumSingularity]

Because the connection on the PSU side is the same. However on the other side it's not. That's why one is labeled CPU or EPS and the other PCIe. So don't try to replace them with one another. As for the GPU, it would be fine. But as i said, you will put your PSU under some proper torture, so better get right to it. It's a good thing it has Platium rating, cause it's gonna spend its time into the 90%+ load almost all the time when you put a proper load on it. Both PSU and GPU have various protection on them, so they would be safe.

[884248]

How would I "do this right"? Should I just get an 850w PSU? 1000w?

[QuantumSingularity]

With 14700k, i would go straight for 1000W. The difference in price between 850 and 1000 is often less than $20, so no point of holding back. Better have some proper reserve. Don't be afraid however to try and run your rig on the PSU once or twice. It WILL be able start it and probably even run Furmark w/o a CPU stress test at the same time. IT's just when you have both components under load that you might experience some of the protections tripping. So just to make sure everything works fine, you will have no trouble as well as browsing the web, watching some movies, playing some light games. When you get to the "heavy lifting" you might start having issues. 

[884248]

OK I will report back once I test things out. Thanks for the help everyone!