motherboard Finding a motherboard that supports 2 GPUs at full PCIe speed for AM5

[Blaspheme]

Budget (including currency): Roughly $3800 USD in total.

Country: Australia

Games, programs or workloads that it will be used for: KVM, Compiling, Programming, Video Editing, Gaming, VR, 3D Modeling, etc.

Other details (existing parts lists, whether any peripherals are needed, what you're upgrading from, when you're going to buy, what resolution and refresh rate you want to play at, etc): 

Wanting to run a KVM virtual machine with PCI passthrough via OVMF. I plan on running Arch Linux as the host operating system, and running Windows 11 as the guest system.

Only wanting to run the AM5 platform, and I plan on using a Ryzen 9 7900. (non X)

My problem is finding a motherboard that can support 2x GPUs. Preferably 2x RTX 4070 Ti's. Every motherboard that I have come across has a full PCIe 5.0 x16 slot that can run in x16 mode, but finding one that can run another graphics card at x16 seems impossible. Maybe I'm missing something. Just can't seem to find a motherboard that can run both GPUs at x16 speeds/lanes. Most seem to throttle down to x4 speeds/lanes. The PCIe version doesn't bother me. I don't care if it's PCIe 4.0. I just need to find a decent motherboard that can support 2x GPUs that run at full speed, but won't break the bank. (I don't exactly want to spend $1000 on a motherboard.)

 

I mostly know all the other parts I plan on using in my system, but am just struggling to find a motherboard that can support my requirements.

 

Thanks for any recommendations/help!

[Needfuldoer]

10 minutes ago, Blaspheme said:

Just can't seem to find a motherboard that can run both GPUs at x16 speeds/lanes.

AM5 only has 24 PCIe Gen5 lanes, and they're generally split 16x for the GPU, 4x for an SSD, and 4x for the chipset. If you need more than that, you're in HEDT ThreadRipper/EPYC/Xeon territory.

 

I'm not aware of any motherboards with the onboard logic to cram 32 Gen4 lanes through 16 Gen5 lanes. Theoretically there's enough bandwidth available, but dual GPUs has been dead in the gaming space for years and anyone doing high end work that requires multiple GPUs buys an Epyc or Xeon anyway.

 

This is one reason why I went x99 for my new home server instead of building a new platform. I needed a GPU for Plex, a 10 gig NIC, a SAS HBA, and a couple PCIe SSDs, and the Xeon has room for them all in its 40 Gen3 lanes.

[PDifolco]

5 minutes ago, Blaspheme said:

Budget (including currency): Roughly $3800 USD in total.

Country: Australia

Games, programs or workloads that it will be used for: KVM, Compiling, Programming, Video Editing, Gaming, VR, 3D Modeling, etc.

Other details (existing parts lists, whether any peripherals are needed, what you're upgrading from, when you're going to buy, what resolution and refresh rate you want to play at, etc): 

Wanting to run a KVM virtual machine with PCI passthrough via OVMF. I plan on running Arch Linux as the host operating system, and running Windows 11 as the guest system.

Only wanting to run the AM5 platform, and I plan on using a Ryzen 9 7900. (non X)

My problem is finding a motherboard that can support 2x GPUs. Preferably 2x RTX 4070 Ti's. Every motherboard that I have come across has a full PCIe 5.0 x16 slot that can run in x16 mode, but finding one that can run another graphics card at x16 seems impossible. Maybe I'm missing something. Just can't seem to find a motherboard that can run both GPUs at x16 speeds/lanes. Most seem to throttle down to x4 speeds/lanes. The PCIe version doesn't bother me. I don't care if it's PCIe 4.0. I just need to find a decent motherboard that can support 2x GPUs that run at full speed, but won't break the bank. (I don't exactly want to spend $1000 on a motherboard.)

 

I mostly know all the other parts I plan on using in my system, but am just struggling to find a motherboard that can support my requirements.

 

Thanks for any recommendations/help!

AFAIK no chipset supports double 16x lanes ... Best you can get is double x8 on PCie4 (that's what I can do on my X570 AM4 board), maybe you can get double 8x on PCie5 on hi end X670E, look at Gigabyte boards (they often offer more/bigger PCie slots)

[Somerandomtechyboi]

What about going for a mobo that can bifurcate the x16 gen5 to x8 gen5? x8 gen5 is the same bandwidth as x16 gen4 so still sufficiently fast for any gpu even top end ones

[Needfuldoer]

3 minutes ago, Somerandomtechyboi said:

What about going for a mobo that can bifurcate the x16 gen5 to x8 gen5? x8 gen5 is the same bandwidth as x16 gen4 so still sufficiently fast for any gpu even top end ones

The 4070ti is a Gen4 card, so it would effectively run each card at Gen4 x8 in that configuration.

[jaslion]

Fyi gaming in a vm means basically ANY online game will ban you/prevent you from playing due to anticheat.

 

 

Whats the reason for 2 systems?

 

3800$ is enough money to literally build 2 computers on their own.

[Blaspheme]

25 minutes ago, Needfuldoer said:

AM5 only has 24 PCIe Gen5 lanes, and they're generally split 16x for the GPU, 4x for an SSD, and 4x for the chipset. If you need more than that, you're in HEDT ThreadRipper/EPYC/Xeon territory.

 

I'm not aware of any motherboards with the onboard logic to cram 32 Gen4 lanes through 16 Gen5 lanes. Theoretically there's enough bandwidth available, but dual GPUs has been dead in the gaming space for years and anyone doing high end work that requires multiple GPUs buys an Epyc or Xeon anyway.

 

This is one reason why I went x99 for my new home server instead of building a new platform. I needed a GPU for Plex, a 10 gig NIC, a SAS HBA, and a couple PCIe SSDs, and the Xeon has room for them all in its 40 Gen3 lanes.

That sounds like a pretty solid option, but was hoping that there was some possible way of running a regular desktop chip instead of a Workstation CPU. Seems that I might have to go that route, though. Just seems overkill to go Threadripper when I won't be running any loads greater than what a 5950x could handle perfectly.

[Blaspheme]

25 minutes ago, PDifolco said:

AFAIK no chipset supports double 16x lanes ... Best you can get is double x8 on PCie4 (that's what I can do on my X570 AM4 board), maybe you can get double 8x on PCie5 on hi end X670E, look at Gigabyte boards (they often offer more/bigger PCie slots)

I'll make sure to look into that as an option. Thanks for the help!

[Blaspheme]

24 minutes ago, Somerandomtechyboi said:

What about going for a mobo that can bifurcate the x16 gen5 to x8 gen5? x8 gen5 is the same bandwidth as x16 gen4 so still sufficiently fast for any gpu even top end ones

Never really knew that this was a thing, so I'll make sure to check into this. Thanks for the advice.

[Blaspheme]

16 minutes ago, jaslion said:

Fyi gaming in a vm means basically ANY online game will ban you/prevent you from playing due to anticheat.

 

 

Whats the reason for 2 systems?

 

3800$ is enough money to literally build 2 computers on their own.

Yeah, I understand that gaming on a VM pretty much means that most modern games with anticheat won't work. The way I had planned to setup my system was to be able to have Windows installed on another physical drive, so for games like that, I could specifically boot into Windows for the games that required it. That way, I could KVM both machines, but dual-boot when absolutely necessary.

Main reason for wanting to run 2 systems on 1 is that I really don't have a need for 2 separate systems. It just seems like a waste to me, when I mainly run Linux as my main OS, but still use Windows for things like Adobe Suite, 3D modeling, gaming, etc.. The ease of running both systems on one machine is a really niche way of fixing that problem for myself, as I get the best of both worlds.

[Blaspheme]

23 minutes ago, Needfuldoer said:

The 4070ti is a Gen4 card, so it would effectively run each card at Gen4 x8 in that configuration.

I'll also make sure to search this up. Thanks for the info!

[NF-A12x25]

no need to respond 5 times, multiquote makes it so 1 post will suffice

[Blaspheme]

16 minutes ago, NF-A12x25 said:

no need to respond 5 times, multiquote makes it so 1 post will suffice

Sorry about that, new to the site.

I also think I finally found a motherboard that suits my requirements, but would appreciate some feedback, just to make sure I'm on the right track.
Found this: https://www.msi.com/Motherboard/MPG-X670E-CARBON-WIFI/Specification.
It's the MSI MPG X670E CARBON WIFI.

As far as I can tell, it supports a configuration of: x16/x0/x4, x8/x8/x4
over the 3 onboard PCIe x16 slots.
From the chart above, as far as I understand this motherboard should be perfectly compatible with my requirements of running 2x GPUs.
Am I correct in my thinking?

[Stahlmann]

9 minutes ago, Blaspheme said:

Sorry about that, new to the site.

I also think I finally found a motherboard that suits my requirements, but would appreciate some feedback, just to make sure I'm on the right track.
Found this: https://www.msi.com/Motherboard/MPG-X670E-CARBON-WIFI/Specification.
It's the MSI MPG X670E CARBON WIFI.

As far as I can tell, it supports a configuration of: x16/x0/x4, x8/x8/x4
over the 3 onboard PCIe x16 slots.
From the chart above, as far as I understand this motherboard should be perfectly compatible with my requirements of running 2x GPUs.
Am I correct in my thinking?

This motherboard only supports x8 per GPU when 2 are used. And since your GPU's won't support PCIe 5.0, they will run in PCIe 4.0 x8. But most GPUs have minimal performance loss when only running at x8 speeds on PCIe 4.0.

[PDifolco]

1 hour ago, Blaspheme said:

Yeah, I understand that gaming on a VM pretty much means that most modern games with anticheat won't work. The way I had planned to setup my system was to be able to have Windows installed on another physical drive, so for games like that, I could specifically boot into Windows for the games that required it. That way, I could KVM both machines, but dual-boot when absolutely necessary.

Main reason for wanting to run 2 systems on 1 is that I really don't have a need for 2 separate systems. It just seems like a waste to me, when I mainly run Linux as my main OS, but still use Windows for things like Adobe Suite, 3D modeling, gaming, etc.. The ease of running both systems on one machine is a really niche way of fixing that problem for myself, as I get the best of both worlds.

Won't a single dual boot system work as well then?

[Blaspheme]

10 hours ago, Stahlmann said:

This motherboard only supports x8 per GPU when 2 are used. And since your GPU's won't support PCIe 5.0, they will run in PCIe 4.0 x8. But most GPUs have minimal performance loss when only running at x8 speeds on PCIe 4.0.

If it's only a slight performance knock, I won't be really upset about that. As long as it doesn't seriously restrict a RTX 4070 Ti/4070 combo, then I think everything will be perfectly okay.

9 hours ago, PDifolco said:

Won't a single dual boot system work as well then?

Well, the point is to be able to use both systems at the same time, as I very often switch between both OS's, and having to change between the two constantly is rather annoying. Gaming is only my second priority, so I don't mind having to switch between OS's for playing games that require anti-cheat running on the system.