Old Corsair HX520 - Powering x2 3070?

-Ad- · 18 Feb 2021 at 15:53

Hey,

I have an old Corsair HX520W which is around 10yrs old. It's a decent PSU even though it's an oldy but I have a question regarding power x2 3070 and PCI-E risers (it's a 2nd PSU for the GPUs and risers only)

It comes with x2 6-pin ports (with 6+2 cables) then a selection of standard Molex ports.

It does 520W at 80-85% efficiency and has x3 12V rails that can provide 480W (40A). The 3070s have a TDP of 220W each (440W total), then there's the riser cards to consider, but the 3070 cards will be undervolted to around 120-130W in actual usage.

Could this be used to power x2 3070 GPUs in a configuration like so:

3070 1 - 8-pin 1 = 6pin - 6+2pin cable
3070 1 - 8-pin 2 = Dual Molex - 6+2pin cable
PCI-E Riser 1 = Molex - Molex

3070 2 - 8-pin 1 = 6pin - 6+2pin cable
3070 2 - 8-pin 2 = Dual Molex - 6+2pin cable
PCI-E Riser 2 = Molex - Molex

Thanks

mickyflinn · 18 Feb 2021 at 17:03

Each 6 pin psu to dual 8pin pcie cable should be rated as such for that why not use both cables for the gpu,s ?

-Ad- · 18 Feb 2021 at 19:30

Just a 6 pin to dual 8 pin adapter, then no need for molex adapters also?

I think I'll have to try one card first and find out the power draw, then do some calls for current draw on the supplied cables to ensure they're able to take the current.

Thanks.

pc-guy · 20 Feb 2021 at 17:03

What motherboard and CPU are you using? Is this a mining rig setup or a PC setup. If you are plugging those into a PC with normal motherboard and a 65w TDP CPU and a few fans, you better add another 100w to the budget.

also I think the system will draw quite a bit of power during the initial power up. My PC idles around 120w but when it initially boots it takes 290w from the wall for a few seconds that’s very close to the GPU working at full pelt.

So I think you will have troubles. You will end up blowing that PSU on boot.

if you really want to use that PSU you need to do BIOS mod of the GPU. Which probably doesn’t exist as the cards are so new.

-Ad- · 21 Feb 2021 at 12:04

Using my old gaming pc which a i5 s500k Socket 1155.

No issues so far and everything works well.

I just logged some actual power readings from the wall during boot and when being used, did a few calcs for the GPU power cables whilst monitoring voltages at each 8-pin plug, but most importantly everything is well within a safe range of the 520W max output of the PSU with a nice big safety factor of 25%