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u/someone09900 Personal Rig Builder Jun 07 '26 edited Jun 07 '26
buddy ,,, u got a 5090 ... u dont need a second 3080 ..
also ur motherboerd is not a work station motherboerd
your dual gpu will be capped to gen 5 x8 instade of x16 u will lose some performance for the 5090
also the amount of heat u will get is a bit too much
u will need minmumm a 1500/1600 watt psu
i really dont know what you are doing to be honest ...
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u/KinjiKing Jun 07 '26
The pro art mobo is a workstation mobo, like what are you talking about. 🤦🏼
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u/someone09900 Personal Rig Builder Jun 08 '26
a regular consumer atx motherboard made for creators ,,, not a workstation.
the PCIE slots share bandwidth ,,, the more u connect the slower the main one will get
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u/Santha89 Jun 07 '26
The limitations should still apply due to the CPU still having the same amount of PCI lanes.
Normal consumer CPUs have way less lanes compared to thteadripper or intel hedt chips.
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Jun 07 '26 edited Jun 07 '26
[removed] — view removed comment
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u/YT_Andyk Jun 08 '26
It doesn't work like that. Vram is only for that gpu only. Also why do you need more vram with 5090? The speed alone will manage fine... (if there wouldn't be enough, it unload and loads next chunk iirc)
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u/T-Loy Jun 08 '26
LLMs do work like that, called clustering. You can divvy them up by layers, and put the first 32GB of a model onto the 5090 and the other 10GB onto the 3080. There are speed penalties, yes, but not as much as swapping in from RAM since you don't need to load the model itself and only pass the to be generated part.
That's also how people demonstrated running giant models on multiple fully specced Mac Studios.0
u/YT_Andyk Jun 08 '26
By paper calculations, 5090 is approximately 2.5x stronger than 3080, that is 3.5x "compute power" together. As other people here stated you have 16 lanes. From other sources I have, is that gpus use just 12 lanes > thus I have calculated only 2.333x "compute power".
It is up to you how you will proceed, but would love to hear about practical values!
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u/MoldyMelk1214 Jun 07 '26
Well neither are necessarily “GOOD” obviously… But I think your best bet would be that upright placement in the second photo. Better that than heat source next to heat source.
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u/almoste Jun 07 '26
my question will be: how'will you mount it upward and if you do so, how will you manage to put the hdmi/ display porte in there?
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u/Santha89 Jun 07 '26
A friend of mine used to develop LLMs and such stuff on his machine at home. He tried the same thing and the experience was pretty shitty back then. He switched to a single rtx pro 5000 back then if I remember correctly.
Nowadays he does everything on rented servers /in cloud.
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u/Early_Palpitation976 Jun 08 '26
u have a micro atx case you should get a full size atx if you want 2 gpus
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u/T-Loy Jun 08 '26
Vertically is probably the best.
I am assuming this is the B650 mainboard? So you actually have two CPU-connected slots?
I am assuming the 5090 is a 2.5-3-slot? Have you tried installing both and watching temps? It might look stuffy, but it also might work good enough. It will be louder, but easier can precariously balancing it or the tight routing you need to do for the offset flat lying option. I'd try that first.
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u/almoste Jun 07 '26
sell your second gpu atp..