A quick question regarding a PSU

[Jonathan93102 3]

Hello all, 

I know very little about the insides of computers and building them. I am upgrading my Graphics Card to a 3090 24GB card and a new i9 CPU. I’ve found a computer store near to where I live who are going to undertake the work for me. The store have said for my new Graphics Card I need a good PSU with 3 8 pin connectors. I have spent the whole day trying to get a clear answer on whether my PSU can support the new graphics card but I’ve had no luck. 

The PSU I have currently is the Corsair RM850x 80 PLUS Gold 850W

Would someone be able to tell me if this PSU has 3 8 pin connectors for my new GPU?
 

The new graphics card I’m going to be installing is the MSI GeForce RTX-3090-GAMING-X-TRIO-24GB GDDR6x PCI-Express Graphics Card

The new CPU I’m going to be installing is the Intel Core i9 9900K, S 1151, Coffee Lake Refresh, 8 Core, 16 Thread, 3.6GHz, 5.0 ghz Turbo

 

Thanks for your time,   
 

Jonathan 

 

 

 

 

[Bob Scott 7,181]

The RM850x ships with three 6+2 PCIe cables (I have one in my portable simming rig).  It is a modular supply, and it has four suitable sockets for the 8-pin PCIe cables and/or a 4+4 CPU cable.  If you bought the PSU at retail and kept the unused cables, you should have enough of them.  If the PC was built by someone else, they may or may not have given you the extra unused cables when you got the PC.  In any event, you can buy these PCIe cables from Corsair. 

Do *not* let the shop use two connectors on any one cable (they come with two connectors daisy-chained together on each cable)--you need three separate power cables to carry the current needed for the card.

 

[Jonathan93102 3]

1 minute ago, w6kd said:

The RM850x ships with three 6+2 PCIe cables (I have one in my portable simming rig).  It is a modular supply, and it has four suitable sockets for the 8-pin PCIe cables and/or a 4+4 CPU cable.  If you bought the PSU at retail and kept the unused cables, you should have enough of them.  If the PC was built by someone else, they may or may not have given you the extra unused cables when you got the PC.  In any event, you can buy a third VGA cable from Corsair or Amazon. 

Do *not* let the shop use two connectors on any one cable--you need three separate power cables to carry the current needed for the card.

 

Hello, 

Thanks for getting back to me. 

I bought the PC from a company so I don’t have the required cables. I’m sure the shop would know what they are doing I hope. So if I need 3 8 pin connectors would you be able to find a link for the correct cables I need to purchase please? 

I am out of my depth with all this, I haven’t a clue what it all means. 

Would this PSU be able to run the new GPU and CPU with the correct cables is basically what I’m wanting to know or would I need a new PSU. 

Many thanks, 

Jonathan 

[Bob Scott 7,181]

You're a bit in the gray area with a 3090 and an 850W supply.  I've seen people with 750W PSUs reporting problems with 3090 stability...personally I'd want more margin than that, especially with a factory-overclocked GPU that's designed for triple power cables like that one.  My portable rig with the RM850x is an i9-9900K with a 1080Ti.  I run a 1000W PSU in my main simming computer, which is an i9-10900K with a mildly factory-overclocked (1725MHz) 3090.

I'm not in the UK...probably best to let your shop find the cables for you in the EU if you stay with the RM850x.

 

[martin-w 2,977]

9900K is only about 130 Watts max though, much less than a 10900K. So an 850 Watt PSU would probably suffice for the OP. I agree though, I would feel more comfortable with a 1000 Watt PSU. 

Good PSU calculator below.

https://outervision.com/power-supply-calculator

As for PCIe cables, contact Corsair directly. Or companies like Cablemod will make up the cables for you. Best bet is to ask your PC shop as w6kd said. Then the responsibility is theirs. 

Looks like the ones you want are Type 4.

https://www.corsair.com/us/en/psu-cable-compatibility

Scan UK have Type 4, but only for pre order.

https://www.scan.co.uk/products/corsair-premium-individually-sleeved-6plus2pin-pcie-single-connector-cables-type4-gen4-white-and-bla

WARNING: Don't trust my brief googling, check for yourself that Type 4 are the ones you want for your PSU. Incorrect pin outs with PSU cables can cause damage. 

 

Edited February 10, 2021 by martin-w

[martin-w 2,977]

5 hours ago, martin-w said:

 I agree though, I would feel more comfortable with a 1000 Watt PSU. 

 

 

I should add, that I too have seen reports of  transient voltage spikes with the 3090, and issues with OCP cutting in with 850 Watt PSU's, that go away with a 1000 Watt PSU. 

 

Edited February 10, 2021 by martin-w