Thank you!
And you mean to put both RTX 3090 to the first and second slots that are integrated in the CPU (the white ones)? Or you mean first GPU to the first slot and the second GPU to the third slot (which is integrated in the Chipset)?
If you mean the option 1, then there will be no free space between the GPUs, because each RTX 3090 has 60mm width. Right?
If you mean the option 2, then it can be slower, if I understand well.
The last slot is not to be used for gpus. Only 4 gen3 lanes there.
There are 3 slots worth of space. If you do have 3-slots cards, you should indeed look for mainboards with 4-slots spacing.
I had in mind my blowers, which are just 2-slot wide. Apologies.
Hi @balnazzar,
I have just purchased 2x GIGABYTE GeForce RTX 3090 24GB TURBO blower cards due to the recent announcement that they are no longer being produced. Now I just need to build the PC around these two cards… I am hoping to be risk-averse in this build and would ideally like to build a rig almost part for part that someone else has built before. Either your 2x3090 or the rig that @greent built after your recommendations (Recommendations on new 2 x RTX 3090 setup) would be ideal.
I couldn’t actually find a part list for your 2x RTX 3090 build. Do you happen to have either a https://pcpartpicker.com/ link or a parts list for what you yourself ended up building?
Thank you, massively appreciated,
Simon
[EDIT]
I was able to find one of your builds detailed! 
Is this the build where you added in your two RTX 3090 blower cards?
[/EDIT]
Hi! No, that Threadripper is doing something else…
My build is pretty simple: essentially a Xeon 8260M upon an Asus pro WS C621-64L SAGE/10G, with four 32gb rdimms and a couple PM1735 ssds. The psu is a Corsair HX1200i.
However, if you prefer a TR, go for it. That machine you linked was built with the perspective of putting 2-3 gpus in it in the future.
Hi @balnazzar,
Thank you, I massively appreciate the detailed list.
After looking at your system, and trying to bring the price down a bit I think I’d like to go down the Ryzen route as you recommended in the following places:
Which gives me the following items (also copying your case):
So I’m going to see if I can fill out the rest of the specs based on this system foundation. If you had strong recommendations for RAM on an AMD system I’d be keen to hear that.
[EDIT]
I found your AMD RAM recommendations at the previously posted blog:
[/EDIT]
So for the other components:
The only observations that come to my mind are:
The Vision D is a great board, but as it has been highlighted by the user above, it got 3-slot spacing between the cards. That mean you got to use a bridge for the A6000 if you want to NVlink them. Check (or ask Nvidia) for compatibility.
Take at least one pcie 4.0 ssd. Not that it will make much difference for DL-related tasks, but they are only marginally more expensive than 3.0, and they’ll make you system more reactive.
Prices are overinflated right now. Consider buying second-hand parts or previous generation parts, particularly the cpu (a r3000 will do just as fine as a r5000).
Enjoy your build!
Thanks for those tips.
I figure the 3-slot spacing would be quite beneficial for thermals though? I would be quite surprised if the the 3-slot spacing NVLink bridge didn’t work for the RTX 3090. I’ll look into it.
Yup, good call. I’ll make that change.
Yup good call. I’ll consider swapping our for an R3000.
Sorry for missing the message earlier.
Thanks @balnazzar. Actually the 3090 is running at 14 TFops. However, the “older gens” were running at lower clock speeds. I’ve just upgraded my drivers and now all cards are actually running at the same clock speeds.
Phew, no need to replug anything (Andrea knows how much that scares me 
)
I’ve decided to water cool my 3090 Turbo as it is too loud. I’ve already received water block, pump, radiator, etc… but I need to get a new case as my current one is too small.
Do you have any recommendations for good cases for water cooling 2x3090? I have one 360mm radiator that is 45mm thick, and will add a second one (or a 240mm?) to the custom loop when I get my second 3090 later this year.
The usual ones… The Dynamic XL, the Define 7 XL, the Dark Base 900, and a few others.
Hi @balnazzar,
Thank you for all of the back and forth on this one. Just so that it’s all in one place, here’s my refined build list based on feedback and some other considerations. All prices in AUD.
That’s a 4-slot bridge. You need a 3-slot, with the b550 vision D.
The rest is fine!
Yup, thanks. Silly me. I bit more searching, it seems 3-slot 3090 NVLinks aren’t actually for sale anywhere. But they are coming:
So, I have adjusted the above list with an edit to reflect that change.
Thank you @balnazzar for all your help on this one. 3D Medical Imaging U-Nets here I come!
Is there any comparison out there between 2x3090 with and without NVLinks bridge? I’m wondering how much will be the impact on deep learning applications.
I want the bridge so that I can train networks where even one dataset being trained at a time might need > 24 GB of RAM. So for me personally it’s a matter of the bridge increasing flexibility on what I can do, not so much a speed question.
What are your thoughts regarding swapping out the CPU for the Ryzen 7 5800X?
You can do it even without the NVLink bridge. The difference it that the GPUs won’t be forced to communicate through the PCIe bus (that is, passing through the cpu, which slows down the process).
@dvachalek if you really put the gpu @350W under continuous stress (not timespy/furmark, and not even DL training, but gpu_burn or a mining sw) then the vrams will approach 110C.
Putting heatsinks upon the backplate does help, given that you have sufficient ventilation and case airflow, but not by much. The solution? Use your GPU at 260-280W. You won’t sacrifice much performance, and your temps will stay under 100C. Particularly if you already installed additional heatsinks.
Want to use the gpu at 350W no matter what? Then go liquid. Maybe install a ram waterblock on the backplate too… This will solve the ‘problem’ once and for all.
Remember that such a gpu is sold as a gaming gpu. And indeed Nvidia did cut 50W from the a6000, also using the slower gddr6. Note that the a6000 is not driver capped, but it is often inferior to the 3090 in DL benchmarks.
What I’m saying here is that two 3090s do cost almost half a single a6000 while providing a lot more perf even if used at reduced wattage.
right now two 3090 (~2700 € per GPU) cost the same as one A6000 (~5400 €) at least in germany. How does a A6000 compare to two 3090?
On the other hand:
See above. Maybe, given your requirements, one a6000 would be preferable.
That’s indeed the case, at least in my experience.
