Question 2xRTX 3090 on an ASUS PRIME B450-PLUS

[davide445]

Due a new project (no mining, realtime simulation) I will need to use a single or possibly double RTX 3090.

Since the compute part it's all on the GPU there is no special need for strong CPU, and I can think to upgrade my current PC instead of purchasing an expensive new rig.

Current setup use an ASUS PRIME B450-PLUS as mobo (was made for realtime graphics so not needing something special), with Ryzen 5 2600X and 64GB RAM, 750 W 80+ Gold PSU.

Apart the PSU topic, want to know if someone has an idea if I'm risking in using a so heavy and powerful GPU on this midrange mobo, and if will be actually possible to use two of them with NVLink bridge at need.

 

[sdifox]

Getting the video cards is the hurdle. Also if you can afford 2 3090 you can afford a X570 board. You want more pcie lanes.

 

[davide445]

Will start with one 3090, and will be ok with current PCIe 3.0 x16 slot in the B450 mobo for a start.
Understood two of them make no sense on that mobo considering will work on PCIe 3.0 x8 on one slot and 2.0 x4 on the second, so sure will change it if there will be need for two GPU.

So the question is if I need to look a specific mobo feature to work with NVLink bridge.
NVLink it's not SLI, but reading around some are suggesting to look at SLI certified mobo (I didn't even find anymore the SLI parameter in the estore filters).
Some others write (to me more understandingly) the mobo has nothing to do with NVLink, so you choose considering other things.
So remaining with this doubt.

 

[sdifox]

Will start with one 3090, and will be ok with current PCIe 3.0 x16 slot in the B450 mobo for a start.
Understood two of them make no sense on that mobo considering will work on PCIe 3.0 x8 on one slot and 2.0 x4 on the second, so sure will change it if there will be need for two GPU.

So the question is if I need to look a specific mobo feature to work with NVLink bridge.
NVLink it's not SLI, but reading around some are suggesting to look at SLI certified mobo (I didn't even find anymore the SLI parameter in the estore filters).
Some others write (to me more understandingly) the mobo has nothing to do with NVLink, so you choose considering other things.
So remaining with this doubt.

SLI is dead, NVLink is what you need. I don't think there are actual mb support needed other then the 2 pcie alots.

 

[davide445]

I don't think there are actual mb support needed other then the 2 pcie alots.

That was also my understanding, but will be good if I can find somewhere Nvidia telling this....

 

[Fardringle]

In addition to wanting an X570 motherboard to have enough PCIe lanes for the two graphics cards, you're also going to need a much bigger power supply if you plan to have two of them running under heavy load since the RTX 3090 has a 350 Watt TDP for the reference model, and some companies have changed theirs to use well over 400 watts.

 

[davide445]

Aware of this. Due the fact I'm not sure this will be a permanent setup will probably opt at the beginning to an external secondary supply for the second card, instead of investing into a massive internal PSU that will remain unused most of the time.
A 400w 80+ Gold external PSU its about $60, a 1000+W its x4 the amount.

 

[legolas_tk]

The motherboard's specifications states expansion slots
3rd/2nd/1st Gen AMD Ryzen™ Processors
1 x PCIe 3.0/2.0 x16 (x16 mode)

AMD B450 chipset
1 x PCIe 2.0 x16 (max at x4 mode)

So therefore you can't run 2nd GPU at max speed. The second GPU will run at PCIE 2.0 x16 (actual 4x mode). I recommend using single GPU for maximum performance. secondly, the motherboard only supports AMD CrossFireX™ Technology and not support Nvidia SLI.

 

[davide445]

Sure if using a single GPU current mobo will be ok, with two will need to invest in a better one.
The doubt it's if some special feature/certification is needed due the intended usage of NVLink btw the two one. SLI it's dead and not sure if SLI mobo compatibility certification make any sense related to NVLink.
Seems the mobo didn't care since NVLink its a GPU-GPU communication bus, but didn't find anything specific on this.

 

[Fardringle]

Yes, one card should be fine in that system. Two cards will require some additional upgrades of the motherboard and power supply.

As far as I'm aware, NVLink doesn't require any special motherboard support as long as the board has two full speed PCIe slots for the cards.