HELP: PSU compatibility

[alsebka]

Hey everyone, 

 

this might be a stupid question - but im new to the self build pc world. 

I'm wondering if it is possible to use this PSU: Corsair AX860i with this Motherboard: AsRock Fatal1ty X399 Professional Gaming. The Motherboard needs two CPU Connectors which the PSU has. But it needs one 8 pin and one 4 pin. No idea why this only has 1x8 and 1x4 ... other x399 need 2x8... 

 

and i don't really understand the labeling on the PSU. What are the connectors for the cpu?

Help would be much appreciated! 

 

- Alex

[Jurrunio]

2. PCIe power can CPU power both use the 12V rail, so they use the same sockets on the PSU.

[Herman Mcpootis]

the 8-pin plugs on the right side as the psu has already labeled out.

[Oshino Shinobu]

You can't really tell anything from the PSU end connectors because they're not the same as the motherboard/component end. 

 

The AX860i comes with 2x 4+4 pin EPS/CPU power cables. They're basically 8 pin EPS/CPU but split into two sets of 4 pins on each cable so that they can easily plug into 4 pin connectors too. 

 

Your board likely only needs the 8 pin plugged in, but the 4 pin provides some extra power (that's normally how multiple CPU connectors works). 

 

Basically, the PSU will work fine with it. EPS/CPU power cables will plug into the group of 6 PCIe/CPU connectors on the bottom right. 

[alsebka]

Thanks everyone!

[alsebka]

11 minutes ago, Oshino Shinobu said:

You can't really tell anything from the PSU end connectors because they're not the same as the motherboard/component end. 

 

The AX860i comes with 2x 4+4 pin EPS/CPU power cables. They're basically 8 pin EPS/CPU but split into two sets of 4 pins on each cable so that they can easily plug into 4 pin connectors too. 

 

Your board likely only needs the 8 pin plugged in, but the 4 pin provides some extra power (that's normally how multiple CPU connectors works). 

 

Basically, the PSU will work fine with it. EPS/CPU power cables will plug into the group of 6 PCIe/CPU connectors on the bottom right. 

Thanks! I thought that there were dedicated CPU/Motherboard connectors - as seen on some other PSUs. Threadripper seems to need some more power so i guess A 4+4 and a 6+2 should be fine then. 

[iRileyx]

23 minutes ago, alsebka said:

Thanks! I thought that there were dedicated CPU/Motherboard connectors - as seen on some other PSUs. Threadripper seems to need some more power so i guess A 4+4 and a 6+2 should be fine then. 

Use 2 4+4's, though one of them will only need one 4 pin connected on the motherboard side.

 

A 6+2 won't work in a motherboards cpu power plug, 6+2's are meant for graphics cards.

[STRMfrmXMN]

3 hours ago, alsebka said:

Hey everyone, 

 

this might be a stupid question - but im new to the self build pc world. 

I'm wondering if it is possible to use this PSU: Corsair AX860i with this Motherboard: AsRock Fatal1ty X399 Professional Gaming. The Motherboard needs two CPU Connectors which the PSU has. But it needs one 8 pin and one 4 pin. No idea why this only has 1x8 and 1x4 ... other x399 need 2x8... 

 

and i don't really understand the labeling on the PSU. What are the connectors for the cpu?

Help would be much appreciated! 

 

- Alex

 

I'm not sure why those extra four pins aren't there but from what I understand the extra four pins only provide redundancy. Anyways.

 

TL;DR the AX860i is fine for your system, yes.

[alsebka]

3 hours ago, RKRiley said:

Use 2 4+4's, though one of them will only need one 4 pin connected on the motherboard side.

 

A 6+2 won't work in a motherboards cpu power plug, 6+2's are meant for graphics cards.

Ah okay. But how are they different from one another? Is there really a difference between 4+4, 6+2 and 8 pins? They are just wires, right? 

?‍♂️

[mariushm]

6 pin pci-e is 3 wires for 12v (+), 3 wires for ground (-).

8 pin pci-e is 3 wires for 12v , 5 wires for ground  (the extra 2 wires added to the pci-e 6pin connector edge are just ground wires)

8 pin cpu power is 4 wires for 12v , 4 wires for ground

 

If I remember correctly, the pci-e and cpu power connectors are also reversed .. well, reversed is probably a bad word... one of the connectors has the +12v wires on the top row as you look at the connector with the retention clip at the top, and the other connector has the 12v wires on the bottom row.

 

The holes in the connectors are keyed differently (they holes are not square, some have specific shapes which makes it very hard or impossible to insert the connector the wrong way.

 

Each connector on the power supply is probably 4 12v (+)  and 4 ground (-) pins, which makes it easy to wire 8 pin cpu power connectors to it.

 

-

 

The ATX standard says a 4 pin cpu connector must be capable to accept up to 8A per circuit (pair of wires), so you have 2 x 8A x 12v = 192 watts maximum allowed.

For a 8 pin connector, the standard allows for maximum 7A per circuit (it's lower because it's more pairs of wires closer together), so you have 4 x 7A x 12v = 336 watts.

 

Threadripper processors have a 180w TDP and can probably consume up to 250 watts in some specific cases, basically when you abuse them with benchmark programs like prime95

For brief moments (milliseconds), the processor may take a bit more than 250w, let's say up to 300w

 

This is the reason why you need 2 power connectors. In theory, even with 300w of power consumption, one 8 pin connector would be enough, but in general it's better to be safe than sorry and leave some room and not worry about connectors overheating (which happens when too much power goes through connectors)

With two connectors, there's only around 125-150 watts going through each connector, with lots of room to space and everyone's happy (except people with power supplies that have only one power connector)

[alsebka]

1 hour ago, mariushm said:

6 pin pci-e is 3 wires for 12v (+), 3 wires for ground (-).

8 pin pci-e is 3 wires for 12v , 5 wires for ground  (the extra 2 wires added to the pci-e 6pin connector edge are just ground wires)

8 pin cpu power is 4 wires for 12v , 4 wires for ground

 

If I remember correctly, the pci-e and cpu power connectors are also reversed .. well, reversed is probably a bad word... one of the connectors has the +12v wires on the top row as you look at the connector with the retention clip at the top, and the other connector has the 12v wires on the bottom row.

 

The holes in the connectors are keyed differently (they holes are not square, some have specific shapes which makes it very hard or impossible to insert the connector the wrong way.

 

Each connector on the power supply is probably 4 12v (+)  and 4 ground (-) pins, which makes it easy to wire 8 pin cpu power connectors to it.

 

-

 

The ATX standard says a 4 pin cpu connector must be capable to accept up to 8A per circuit (pair of wires), so you have 2 x 8A x 12v = 192 watts maximum allowed.

For a 8 pin connector, the standard allows for maximum 7A per circuit (it's lower because it's more pairs of wires closer together), so you have 4 x 7A x 12v = 336 watts.

 

Threadripper processors have a 180w TDP and can probably consume up to 250 watts in some specific cases, basically when you abuse them with benchmark programs like prime95

For brief moments (milliseconds), the processor may take a bit more than 250w, let's say up to 300w

 

This is the reason why you need 2 power connectors. In theory, even with 300w of power consumption, one 8 pin connector would be enough, but in general it's better to be safe than sorry and leave some room and not worry about connectors overheating (which happens when too much power goes through connectors)

With two connectors, there's only around 125-150 watts going through each connector, with lots of room to space and everyone's happy (except people with power supplies that have only one power connector)

Wow thanks! That's really interesting, more detailed I have hoped for and informative! I thought that maybe the top row of each connector would be VCC and the bottom would be GRN. This would have made it fully modular. 

 

Building a Pc from scratch is more complex than I thought. Ryzen doesn't make it easier tho.