Advice for fitting 2nd RTX 3090?

[anthonyhague]

Im a Apple guy but after seeing David Ariev's Intro to Octane video I saw this might be my last chance to conquer 3D after several previous failed attempts. £8K bought me the computer listed below but the motherboard was selected by the shop who did the build, unfortunately now I find out it has 1x PCIE x16, 1x PCIE x8 and 1x PCIE x4. My 3d mentor tells me if I fit a 2nd 3090 im going to get a lag because its plugged into the x8 PCIE.
RAM, ive found another 2x 32Gb DDR4's same spec for £200 to total 128Gb so that I can utilise the NVLink Bridge for the dual VRAM.

Question: Is it worth me fitting a 2nd RTX 3090 if the PCIE is only x8? Or should I replace the motherboard first?


Thanks for any advice you give in advance, this is my first PC and I know nothing, so please feel free to tell me anything that I might not know to do with getting the best performance.




CPU: Ryzen9 5950X AM4 16x CPU’s
Motherboard: Gigabyte X570M AORUS Master AM4 ATX https://www.gigabyte.com/Motherboard/X5 ... -rev-10#kf
RAM: 64Gb (2x 32gb) Patriot Viper Steel DDR4 3600MHz CL18 1.35v
Hard Drive: Samsung 980 Pro M.2 SSD 2Tb
Internal Backup Drives: Seagate IronWolf SATA 10Gb X2
GPU: GeForce PALIT RTX 3090
PSU: 1000Watt Corsair RM1000X ATX
Fan: Noctua NH-D15S CPU Cooler with NF-A15 PWN 140mm Fan
Case: Fractal Design 7 Black Solid Case
Monitors: BenQ EW3270U 32” x3
Wacom: intros Pro Large PTH-860
Keyboard : Logitech G815
Mouse: Logitech MX Keys

[glimpse]

good day,

Question: Is it worth me fitting a 2nd RTX 3090 if the PCIE is only x8? Or should I replace the motherboard first?

yes, adding second 3090 will cut Your render times exactly in half, so what takes You 10 will take just 5min.

most motherboards go to dual x8 so no problem here -there will be no difference at all in rendering speed or such.

as for mobo itself.. it has triple slot spacing, and depending on GPU You have, You might have issue cooling top one, as it's fans might touch the card under.

what is the exact GPU You have? Could You send a link?

the last but is Your PSU, that could be a bit too small to have stability under load.

[anthonyhague]

Thanks for your help man. Any suggestions for cooling would be greatly appreciated.

I don't have the box as I got it used but I took it out of the case and photographed the serials for you. All I know is its a PALIT 3090 apart from that, I hope this gives you what you need?

[glimpse]

is it this card?

https://global.microless.com/product/hp ... 24410-002/

[anthonyhague]

https://www.ebay.co.uk/itm/144292375982 ... SwItphl8sQ

Its a PALIT, that's all I know mate

[glimpse]

so, if You want to use 2 cards with NVLINK, they better have completely the same high and NVLINK placement. Depending on PCB, those 3090s do vary quite a bit.

however if You think Your projects would fit inside 24GB skip second card being the same and get smth like blower or hybrid cooler equipped GPU. Otherwise, with two of the same cards side by side in the motherboard You have would lead to issues for sure - tip card would run quite a bit more hot and that could negatively influence stability, not to mention performance itself.

if I were You would go for slightly more expensive A5000 as it is blower and dual slot only + it sips less power. You might be just around what Your PSU offers.

[anthonyhague]

Well I always planned on 2x 3090's from the start, nobody ever told me about this stacking issue. Ive seen David Ariev stacking 4x 2080's and im sure they are cooler etc but this is a bit of a blow.

The NVlink was just an added benefit and another reason to but the same 2nd PALIT 3090.

Can I not improve cooling like fit water cooling or extra fans or something?


Thanks for your advice glimpse

[glimpse]

do not compare cards between generations (1080ti, 2080ti, 3090..) - they get bigger and more power hungry. In the past I built machines with 7x 1080ti, that were comfortably running on 1600W PSU sipping 1400W from the wall (with entire system), later Quad 2080ti and those used probably around 1200W. And lately, if You run 2x 3090s, You need at least 1200W PSU, as 1kW might not be enough to cover spikes.

with power consumption comes all the heat - on the same loop, with same external rad You can handle 7x 1080tis, quad 2080ti or 2-3x 3090s.. hence most of coolers available right now are triple slot thick, or at least 2.5ish..

water-cooling is an option & not the worst one, just calculate what You need to spend. for sure You will need to change the case that supports at least 2x 360 rads with good fans and extra PSU to help feeding Your system.

so, if You want to have second card, the same, try it..but be prepared to spend more if You see overheating issues or power off due to PSU overload.. - in this case You can swap PSU or add the second one. With later, You will need to change the case, but if You are thinking about watercooling, You might want to do that anyway.

[anthonyhague]

Thanks Tom

Im getting my local shop on the EKWB water cooling, Im fine to change the PSU and case etc. Id change the motherboard it it were necessary.

Is it cool if I come back here to show the solution ive been presented with. Just to check you agree its good? Will you be notified?

[glimpse]

sure feel free to share what they offer and I'll try to explain in and outs of such move.

For case, look at smth like O11Dynamic XL, if that suits Your taste visually, as for PSU, I would say go no lower than 1500W (EVGA, Corsair, BeQuiet, SF..) as that would keep PSU at it's optimal load of around 50-60%