GPU's not recognized with pci-e risers

ajrettke33

Limp Gawd
Joined
Dec 7, 2014
Messages
150
So I have 2 setups, both have 2 available pci-e 1x and 2 pci-e 16x slots.

I put GPU's in the 16x slots and used risers for 1x to 16x adapters (powered usb type). On both systems the GPU's in the risers power up (I turn the secondary PSU on right before I startup the main) and the OS never sees them (ubuntu or windows).

I have a bunch of different risers and video cards I've tried interchanging them and still nothing...anyone know what I'm missing?

Thanks,
Aaron
 

Kainzo

Gawd
Joined
Nov 12, 2009
Messages
960
So I have 2 setups, both have 2 available pci-e 1x and 2 pci-e 16x slots.

I put GPU's in the 16x slots and used risers for 1x to 16x adapters (powered usb type). On both systems the GPU's in the risers power up (I turn the secondary PSU on right before I startup the main) and the OS never sees them (ubuntu or windows).

I have a bunch of different risers and video cards I've tried interchanging them and still nothing...anyone know what I'm missing?

Thanks,
Aaron
Got pictures?
 

PiERiT

2[H]4U
Joined
Oct 8, 2010
Messages
2,571
The ones that do work, are they powered by the primary PSU or the secondary? If it's the primary, turning on the secondary PSU right before the primary might not be enough. I use an adapter to turn them on simultaneously:

https://www.newegg.com/Product/Product.aspx?Item=9SIAAK94766757

If the working ones are also on that secondary PSU then I am not sure. There may be some BIOS settings you need to tweak. I'd also try running every card with a riser, even the ones you were plugging straight in, and seeing if that works.
 
Last edited:

DriveEuro

2[H]4U
Joined
Jun 23, 2004
Messages
2,662
What model motherboard.
Some BIOSes have a TOLUD setting. You normally set that to 2.5GB limit. Also, some mobos require you to set PCI-E to Gen 1.
 

sephkeene

Weaksauce
Joined
Mar 14, 2007
Messages
95
The other thing to think about, is are any of your PCIE lanes disabled because you are using them elsewhere? For instance, maybe you have an M.2 SSD in that takes some PCIE lanes away from the add-in slots...
 

Kardonxt

2[H]4U
Joined
Apr 13, 2009
Messages
3,499
To get some mobos to detect gpus using 1x risers I had to short some pins on the pci express slot. I believe it was A1 to B17.
 

DuronClocker

[H]ard|Gawd
Joined
Mar 12, 2004
Messages
1,063
Seems some risers have that A1-B17 short built-in to them already. You can check with an ohmmeter.

If you're having trouble with the 16x slots at all, I've had a lot better luck setting PCIe gen settings to 2-2-2 instead of 2-1-1 as saw widely recommended and forcing the PCIe lane settings to 8x/4x/4x instead of Auto, even when using the 1x-16x risers in those slots. That generally was more for issues with the 16x slots though. I have not had any luck setting the PCI latency to 96 as some suggest. Didn't do a thing for me. In fact, I was fairly convinced that was giving me some trouble over the standard 32 setting.

I've had some risers require the presence pins to be shorted (again, can check your riser cards with an ohmmeter). Could also have a bad riser or USB cable. I haven't had a bad riser card that goes into the PCIe slot, but I have had a handful of the 16x slot parts go bad. Probably somewhere in the 80-90% reliability range for me. I've got 34 running right now, and I've probably had around 5 be DOA or go bad quickly. Had one with a bad USB cable.
 
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