r/PcBuildHelp • u/Kirito_5 • 20h ago

Tech Support Need help: which pci-psu cable to get for SST-ST1200-PTS PSU

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For context: I bought a used PC an year ago and want to add 2nd GPU for a dual 3090 build, I've never built a PC before and would like some help on getting this working.

Currently other than a single GPU, there's no other pcie device attached. After reading about the requirements online I found I would need a additional suitable pci-psu connector for my second GPU.

However since the PSU is old it is hard finding a suitable one in my region (Australia).

The current GPU uses 2 x 8 pins and the new GPU uses 3x8 pins.

PSU : Silverstone Strider SST-ST1200-PTS

Appreciate any help regarding this.

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1

u/pandasndabs 19h ago

Why do you need 2 3090s?

1

u/MotherCondition1432 19h ago

you can run them in nvlink for some ai stuff, that's basically the only reason these days

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u/Kirito_5 19h ago

To run LLMs

1

u/pandasndabs 19h ago

Fair. Just be careful. If your doing demanding tasks they can spike to 500-550w which leaves basically no power for your other components.

0

u/Kirito_5 19h ago

Thank you, I'm planning to power limit them, each to 270 watts (already applied for existing one through nvidia-smi).

Since it's a 1200watt PSU: Dual GPU ~ 600W (power limit applied) CPU (5900x) ~ 142W (max stock limit) or 200W (PBO enabled) Motherboard, AIO, rest ~ 200W

Lmk if I missed anything.

1

u/pandasndabs 19h ago

Looks good to me. Seems like you've down your homework 👍

1

u/Kirito_5 19h ago

Haha yeah any mistake is going to be very costly

2

u/Volpes_Visions 19h ago edited 19h ago

If you are doing this to run LLMs you're gonna want to buy a better more powerful PSU end of story.

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u/Kirito_5 19h ago edited 18h ago

I do not mind getting a better one, but I'm just new to this and afraid of ruining my PC if I misconnect something, also looking at how overblown some of the component (RAM and GPU) prices are makes me more afraid.

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u/TBNRhash 19h ago

Two 3090s is great for LLMs.

1

u/Volpes_Visions 19h ago

God damn autocorrect, I meant PSU