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Third monitor not working since enabling SLI

Red_Machine

Red_Machine

Joined
Oct 1, 2010
Messages
2,365 (0.44/day)
Location
Marlow, ENGLAND
System Specs
System Name Chachamaru-IV | Retro Battlestation
Processor AMD Ryzen 9 5900X | Intel Pentium II 450MHz
Motherboard ASUS ROG STRIX X570-F Gaming | MSI MS-6116 (Intel 440BX chipset)
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Video Card(s) nVIDIA GeForce RTX 4070 FE | 3dfx Voodoo3 3000
Storage 1TB WD_Black SN850 SSD (OS), 3TB Toshiba (Storage), 8TB Seagate FireCuda/2TB WD_Black SN580X (Steam)
Display(s) Samsung Odyssey G5 27" @ 1440p144 & Dell U2412M @ 1200p60
Case SilverStone Seta A1 | Beige box
Audio Device(s) Creative Sound Blaster AE-7, Edifier speakers, Grado Labs SR80 X headphones | Sound Blaster AWE64
Power Supply EVGA Supernova 750 G2 | 250W ASETEC
Mouse MX Master 3S| Microsoft Serial Mouse v2.0A
Keyboard Vortex Race3 | Dell AT102W
Software Microsoft Windows 11 Pro | Microsoft Windows 98SE
I recently purchased a used GTX 580 to pair with my existing one. My original configuration was three monitors, the two biggest plugged into my 580 and the smallest plugged into the motherboard. When I installed the new card, I plugged the two secondary monitors into the new GPU and disabled the onboard graphics. The machine booted up fine and I had display on all my monitors, however as soon as I enabled SLI I lost the third monitor and no matter where I plug it in I can't get a signal.

I know it's not the monitor or the cable, because they both work fine when plugged into another computer, or if I unplug the other secondary monitor. I even re-enabled the onboard graphics, but I still cannot get the third monitor to display anything, even if I plug the larger secondary monitor into the motherboard and the one in question into my original GPU. I don't get it. Can someone help me out here?
 
All of your displays have to be plugged into the same video card when running in SLI.
 
You have to "span" monitors when using SLI, and this isn't possible when using a different GPU for a different display. You'll have to connect all monitors to the VGAs and then enable spanning.

Aquinus said:
All of your displays have to be plugged into the same video card when running in SLI.
Click to expand...

No, that's an AMD thing. You can plug monitors into either card just fine (when running 3 monitors I plug two into the top card, and one into the lower, or when using three GPUs the same, one into each card)... but SLi restricts usage to two displays...one of which can span across multiple monitors.
 
I'm not trying for surround gaming here, I just want two extra monitors to put Skype and AIM on and stuff like that.
 
cadaveca said:
I understand that, but it is not possible due to how the driver works. The only way to do what you want (albeit not exactly what you want) is to use surround w/SLi.
Click to expand...
Not even that but, to use SLI and drive 3 display, you need to have them all plugged into one card. They don't need to be in surround but, they do need to all be plugged into the same GPU.
 
Aquinus said:
Not even that but, to use SLI and drive 3 display, you need to have them all plugged into one card. They don't need to be in surround but, they do need to all be plugged into the same GPU.
Click to expand...
No, they don't. I never have. Running two GPUs and three monitors right this second, two plugged into the top card, one in the bottom. If I enable surround, it works just fine, and I have NEVER plugged more than two monitors into the top card except when I first got the cards.

IF I enable SLI, the monitor connected to the 2nd GPU drops out. When I first got the cards I tried all three on one card, and still.. just two monitors enable.
 
cadaveca said:
No, they don't. I never have. Running two GPUs and three monitors right this second, two plugged into the top card, one in the bottom. If I enable surround, it works just fine, and I have NEVER plugged more than two monitors into the top card.
Click to expand...
So it forces you to do one desktop in SLI? That sounds kind of backwards, don't you think? I understand why it occurs on AMD cards but, it doesn't really make sense the other way around. Either way, you have the cards and I don't but, I suspect that if all 3 were off the same GPU like with an AMD card, it would probably work to drive the 3 independently. He OP said it's disabling a single display when he switches it. I'll concede that in surround it might work fine and might be a nVidia driver thing like eyefinity is but, I still suspect that he could drive all 3 independently if they were all in one card.

I suspect surround support is a driver thing and the SLI messes with Window's ability to use the display on the SLI'ed card whereas surround already screws with the monitor setup. Either way, it's all speculation unless it gets tested.
 
Right now, I have my main monitor plugged into the top 580 and the second monitor plugged into the motherboard. The third monitor is also plugged into the top card, but it doesn't display anything unless I unplug one of the others.
 
Aquinus said:
I still suspect that he could drive all 3 independently if they were all in one card.
Click to expand...
See his post above.

@Red_Machine :

You can try disabling SLI and connecting all monitors to the 580, if possible, and try @Aquinus's suggestion, but I am pretty sure you'll find you're left in the same situation. You can use all the monitors if you disable SLI, correct?
 
I just disabled SLI and now I lost my other monitor too. I'm going to try reinstalling the driver.
 
Reinstalling the driver didn't fix it. Even plugging in ALL the monitors to the top GPU (which is difficult, because the nVIDIA-supplied mini-HDMI to HDMI cable barely reaches) and selecting "Activate all displays" in the nVIDIA Control Panel doesn't make the third monitor work. I remember that back in the day, nVIDIA cards could only power two monitors, but I thought that had been fixed. And besides, I'm trying to use the onboard graphics, surely the card can't interfere with that.
 
Red_Machine said:
I remember that back in the day, nVIDIA cards could only power two monitors, but I thought that had been fixed.
Click to expand...
It wasn't until the 600 series that NVidia cards could drive more than two displays. You, unfortunately, are stuck with two displays per card.
 
But the thing is, I have two cards here that I'm trying to run in SLI. Surely I could run two on one card, and one on the other? It's not even letting me run one of the monitors on the onboard video for crying out loud.
 
Just thought you guys would like an update.

I had a 4am brainwave that maybe it was caused by digital signalling, perhaps enabling SLI somehow gimps your computer to only being able to output 2 digital signals, regardless of where you plug them in. So I decided that in the morning I'd try plugging in one of the monitors via VGA, and viola, it worked. I still don't get why I can't use the onboard graphics for the third digital signal, but at least I have all my monitors working again.
 
Last edited:
Wouldn't say, adding in a little GT210 to run the extra monitors with the 580's still in SLI work? Like

580's = two monitors
210 = extra monitors

Food for thought.
 
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