Should I get a 2nd GPU

[Chantsu]

I currently have a weird niche issue...
I have a custom build with:
-Ryzen 9 5900x
-64GB DDR 4 34000
-Gigabyte 4080 eagle OC
-MSI B550 ACE MEG (This may be wrong am not currently home)
-Triple monitors w/ VR (this is important)

I am considering adding a 2nd GPU to my build, for a very specific reason, however I do not want to lose my 16x lanes from my primary gpu 0 slot.
The reason behind this is not for more monitors but to tailor to my software need when running my VR headset... The Varjo software has a weird issue when it comes to having more than 2 displays plugged in while launching the software to running my vr. When I launch with all 3 of my monitors plugged into the GPU is asks for one to be unplugged every time, and I have not found any work around this within the Varjo software.

For reference Varjo makes very high end 4k+ headsets that have 2 separate displays in them and are very hardware demanding (I get around 90% GPU usage with 2 screens and the vr on, running a game) from all of the eye tracking and display rendering. Along side this with the about 2 software I run with the Varjo software, VRCFT (VrChat Face Tracking), SteamVR, then of course the game I am playing. I do not think these software's are any extra strain or even my third monitor, but it seems there is not a work around and it is kind of forcing my hand when I know my GPU can handle all of it, it seems to not let me anyways.

I was considering getting a small 1050 card or similar to run my other 2 monitors while keeping my main 4k and vr plugged into the 4080.

Do you think this is a good choice to solve this issue or should I try to find a work around someway else.

 

[ki8aras]

no this looks like a reasonable solution imo

[Tetras]

10 minutes ago, Chantsu said:

however I do not want to lose my 16x lanes from my primary gpu 0 slot.

We'd need to know the exact motherboard model. I think most B550 boards do not use the graphics lanes for their second full length PCI-E slot, but e.g. the Tomahawk shares lanes between the secondary PCI-E slots and the second M.2 slot.

 

15 minutes ago, Chantsu said:

Do you think this is a good choice to solve this issue or should I try to find a work around someway else.

It could lower performance in some things on the second/third monitors, but I assume you're aware of that. I know AM5 supports passthrough (undocumented) from the integrated display, but you don't have graphics with the 5900X anyway.

[Chantsu]

16 minutes ago, Tetras said:

We'd need to know the exact motherboard model. I think most B550 boards do not use the graphics lanes for their second full length PCI-E slot, but e.g. the Tomahawk shares lanes between the secondary PCI-E slots and the second M.2 slot.

Just look at my mobo, and it is a MSI x570 ACE MEG
I do not think I will run into too much issues as long as I maybe move my m.2's but It is a concern

[tkitch]

https://www.ebay.com/itm/156230422192?epid=11051623173

 

Get a PCIE x4 card like this, and you won't run any risk of your main card losing the x16.

[Tetras]

47 minutes ago, Chantsu said:

Just look at my mobo, and it is a MSI x570 ACE MEG

X570 motherboards are different to B550 in this respect.

 

2 of your PCI-E full length slots DO share the graphics lanes, when both are occupied they will run with 8 lanes each only.

1 of your PCI-E full length slots (bottom slot) supports 4 lane operation and does not use any graphics lanes.

 

47 minutes ago, Chantsu said:

I do not think I will run into too much issues as long as I maybe move my m.2's but It is a concern

From what I can see, this is not necessary, because your M.2 slots don't share lanes with the PCI-E slots.

[igormp]

43 minutes ago, Chantsu said:

Just look at my mobo, and it is a MSI x570 ACE MEG
I do not think I will run into too much issues as long as I maybe move my m.2's but It is a concern

As per the manual: https://download.msi.com/archive/mnu_exe/mb/E7C35v1.2.pdf

 

The last PCIe slot should go through the chipset, so your main GPU will still run at x16 without issues. The NVMes should not have any downgrade in speed, but keep in mind that since 2 of the NVMes and that bottom GPU will go through the chipset (which only has a 4.0 x4 link to the CPU), so if you put 100% load in those 3 all at once you'll see degraded performance, which shouldn't be an issue for regular usage.

[Chantsu]

51 minutes ago, tkitch said:

https://www.ebay.com/itm/156230422192?epid=11051623173

 

Get a PCIE x4 card like this, and you won't run any risk of your main card losing the x16.

didn't even think about 4x card, but this probably the best bet for the fact I wont lose as many pcie lanes, although I probably need to move a m.2 to a gen 3 slot or set the slot to gen 3 speeds instead of 4 may help but I think I may have to sacrifice a m.2 for this issue.

[Chantsu]

26 minutes ago, igormp said:

As per the manual: https://download.msi.com/archive/mnu_exe/mb/E7C35v1.2.pdf

 

The last PCIe slot should go through the chipset, so your main GPU will still run at x16 without issues. The NVMes should not have any downgrade in speed, but keep in mind that since 2 of the NVMes and that bottom GPU will go through the chipset (which only has a 4.0 x4 link to the CPU), so if you put 100% load in those 3 all at once you'll see degraded performance, which shouldn't be an issue for regular usage.

I do anything but regular performance, should I just keep 1 m.2 for my os and stuff while I have the other data transferred/ redownloaded to a regular sata ssd?
Or would throttling speeds on my m.2 lanes work?

basically, asking what would you do xD

[Chantsu]

For reference this is the setup currently 

[igormp]

2 hours ago, Chantsu said:

didn't even think about 4x card, but this probably the best bet for the fact I wont lose as many pcie lanes, although I probably need to move a m.2 to a gen 3 slot or set the slot to gen 3 speeds instead of 4 may help but I think I may have to sacrifice a m.2 for this issue.

Be aware that if you plug anything in the second PCIe slot (even an x1 card), the first slow will downgrade to x8 no matter what.

 

With the 3rd slot you can throw anything in there (even an x16 device) and it'll use at most x4 lanes and won't eat up lanes from any other device.

 

2 hours ago, Chantsu said:

I do anything but regular performance, should I just keep 1 m.2 for my os and stuff while I have the other data transferred/ redownloaded to a regular sata ssd?
Or would throttling speeds on my m.2 lanes work?

basically, asking what would you do xD

I would just slap a cheap gpu on the third slot just for video output and wouldn't touch anything else, in practice it shouldn't make any difference so there's no need to worry.

[Chantsu]

1 hour ago, igormp said:

Be aware that if you plug anything in the second PCIe slot (even an x1 card), the first slow will downgrade to x8 no matter what.

 

With the 3rd slot you can throw anything in there (even an x16 device) and it'll use at most x4 lanes and won't eat up lanes from any other device.

 

I would just slap a cheap gpu on the third slot just for video output and wouldn't touch anything else, in practice it shouldn't make any difference so there's no need to worry.

Alright thank you for this info!