Question What motherboard and case for 2x 4090?

[blazing4181]

What motherboard and case should I get for a 2x 4090 setup? This is for AI and I don't need high performance (bandwidth, lanes) on the second PCIe 16x slot, it is fine if this only operates at 4x. My use case does not need NVLink or SLI.

However, it needs to physically fit on the motherboard. I also need a case that can hold both cards without bumping into anything inside the case. It seems hard to find any good information on this on the manufacturer's website, in the manuals for the motherboards, and reviews also don't seem to test this. It isn't a normal setup, so it isn't that strange.

Will this motherboard work?

https://www.msi.com/Motherboard/MAG-B760-TOMAHAWK-WIFI-DDR4/Specification

Or do I need the second 16x PCIe slot to be at the very bottom of the motherboard?

I can also mention that I'm actually planning on just using my existing 4090 and getting a 3090 as the second card, as the combined VRAM is what matters, and the speed of the second card really isn't important.

If not this motherboard, then maybe something else?

What about the case?

 

[Eximo]

Well, typical 3 slot width GPUs would need at least that much spacing between them. So typical setup for using a cheap ATX board and chassis will work with the 'normal slot spacing. (Second x16 slot should be the 4th slot)

If you get one with an x16 slot on the bottom, then you are going to need a Full ATX chassis so the card can hang past the motherboard. Typical ATX Mid Tower has 7 slots, Some may have 8, but to get a card in the bottom you need 9 expansion card slots.

Now having the cards separated by a good distance should help with cooling and potentially allow you to install other expansion cards.

https://pcpartpicker.com/product/FDJp99/msi-pro-z790-s-wifi-atx-lga1700-motherboard-pro-z790-s-wifi

A board like this one gives you some flexibility:

https://pcpartpicker.com/product/8ncG3C/gigabyte-z790-ud-ac-atx-lga1700-motherboard-z790-ud-ac

 

[Eximo]

Full ATX chassis:

https://pcpartpicker.com/product/FQGhP6/phanteks-enthoo-pro-2-server-edition-atx-full-tower-case-ph-es620pc_bk02#

 

[SyCoREAPER]

I really don't have any meaningful suggestions, just something to keep in mind while the recommendations come in.

Keep spreading in mind. Some may accommodate two 4090s but the gap between then may cook the other if inadequately spaced.

Also cooking should be a priority. So keep that in mind too.

Sorry I don't have any recommendations but wanted to chime in with some keep in mind stuff.

 

[blazing4181]

Well, typical 3 slot width GPUs would need at least that much spacing between them. So typical setup for using a cheap ATX board and chassis will work with the 'normal slot spacing. (Second x16 slot should be the 4th slot)

If you get one with an x16 slot on the bottom, then you are going to need a Full ATX chassis so the card can hang past the motherboard. Typical ATX Mid Tower has 7 slots, Some may have 8, but to get a card in the bottom you need 9 expansion card slots.

Now having the cards separated by a good distance should help with cooling and potentially allow you to install other expansion cards.

https://pcpartpicker.com/product/FDJp99/msi-pro-z790-s-wifi-atx-lga1700-motherboard-pro-z790-s-wifi

A board like this one gives you some flexibility:

https://pcpartpicker.com/product/8ncG3C/gigabyte-z790-ud-ac-atx-lga1700-motherboard-z790-ud-ac

Nice suggestions. Out of these two motherboards, it seems like I could go with either one, or am I overlooking something?

 

[Eximo]

Yes, but the second board lets you adjust up or down a slot and has greater spacing between the first card and second. That second board will need the large chassis as even the highest second slot wouldn't allow a second triple slot GPU in a Mid-Tower. Though an 8 expansion slot chassis would work. However that would place the card as far down as possible which may starve it of air. The larger chassis is better for such power demanding components.

Keep in mind you will also be looking at a pretty big PSU that may limit airflow at the bottom of the chassis.

I would probably take this one:

https://pcpartpicker.com/product/X9...-modular-atx-power-supply-ps-tpd-1600fnfagu-4

Or possibly the cheapest titanium rated for efficiency:

https://pcpartpicker.com/product/hM...ertified-fully-modular-atx-power-supply-bn500

 

[blazing4181]

Yes, but the second board lets you adjust up or down a slot and has greater spacing between the first card and second. That second board will need the large chassis as even the highest second slot wouldn't allow a second triple slot GPU in a Mid-Tower. Though an 8 expansion slot chassis would work. However that would place the card as far down as possible which may starve it of air. The larger chassis is better for such power demanding components.

Keep in mind you will also be looking at a pretty big PSU that may limit airflow at the bottom of the chassis.

I would probably take this one:

https://pcpartpicker.com/product/X9...-modular-atx-power-supply-ps-tpd-1600fnfagu-4

Or possibly the cheapest titanium rated for efficiency:

https://pcpartpicker.com/product/hM...ertified-fully-modular-atx-power-supply-bn500

Nice, many people who do AI that run multiple GPUs tend to limit their GPUs to 250 W, this gives you almost all the performance (in the case of AI LLM inference tasks), but at a significant power saving.

Anyway, what case do you think would work well with the second card (the Gigabyte Z790) when having the second card in the lowest position?

 

[Eximo]

That Enthoo Pro 2 would be my choice. It is one of the cheaper Full ATX out there. Decent airflow.

I run an Enthoo Pro M myself.

Power limiting is something I also practice with my 3080 Ti. Can get about 90% performance at 80% power.