[SOLVED] Which number of cables for the GPU ?

[johnnyboy56783]

Hello everyone,

I have a question regarding PCI-E cables for my Radeon RX 6800 GPU and the new PSU I am tring to install in my system.
What I am confused about is am I supposed to use one or two PCIe cables from the new PSU?

In the previous system (image 03) I had only one cable coming out of my modular PSU in for of "pig tail" and it was connected to the GPU in both of it's connectors (image 01).

As far as I was able to pick up so far we can use one or two cables for the GPU coming out of the PSU.
In the new PSU I have large amount of cables and connectors (image 02).

Now, when I examine the new PSU cable (image 04) I see that it is no different than the connector on image 03.
It also has 12 pins on one end and 2x 6+2 pins on the other (which is equivalent to "pig tail").

Since "pig tail" is not desireable way of connecting PCIe cables (as I understood) and we should use two cables instead I was wondering how exactly should I plug all of this?

Should I take two PCIe cables ant put their 12 connectors in two PSU slots labeled PCIe, while using only one 6+2 connector on the other end for the GPU and leaving the other hanging?

Or I should use only one PCIe cable after all?

Also, there is some note in the instructions about using A or B PCIe plugin in the wiring diagram, and I am not exactly 100% sure that I understand it and how it should be interpreted for both of these scenarios.

Thank you in advance.

Regards,
Johnny Boy.

Images
http://bit.ly/01-radeon-gpu-pcie-connector

02-psu-connectors.jpg

bit.ly

http://bit.ly/03-previous-system-pcie-cable

04-new-psu-pcie-cable.jpg

bit.ly

http://bit.ly/05-psu-technical-data

06-psu-connectivity-and-cable-lengths.png

bit.ly

 

[Eximo]

Well, would have been nice to have the relevant stats for each component.

It is better to have fewer splices and joins on any cable run. More splices and joins is slightly higher resistance which slightly reduces the voltage output at the end of the wire. Not really a big deal.

Some PSUs will warn you about exceeding 250W with a single cable, in which case you just use two, and you leave one connector loose.

Safest to use two cables.

Or buy custom cables without all the extra connections.

 

[Vic 40]

Would just use two cables for best stability.

Only now see what looks to be a Be Quiet lay cable lay out, think with 10 pins output and two cables coming out of that you'd be fine. Would pick a 10pin must be 12 pin slot on the psu side that says it has it's own dedicated rail like the connectors with 12V3 and 12V4 next to it.

the other three pcie connectors seem to share rails.

 

[--SID--]

10pin slot on the psu side

10 pin is P8 (EPS). PCI-e is 12 pin.

 

[johnnyboy56783]

Well, would have been nice to have the relevant stats for each component.

It is better to have fewer splices and joins on any cable run. More splices and joins is slightly higher resistance which slightly reduces the voltage output at the end of the wire. Not really a big deal.

Some PSUs will warn you about exceeding 250W with a single cable, in which case you just use two, and you leave one connector loose.

Safest to use two cables.

Or buy custom cables without all the extra connections.

Hello everyone and thank you for such a promptly answers

@Eximo
Sadly custom cables are not an option at the moment, so I will need to figure this out with the one's which came in the box.
So, if I understood correctly use two separate PCIe cables, plug one 6+2 part in one GPU slot, and leave other 6+2 part of one cable hanging, repeat the step with another PCIe cable, correct?

Would just use two cables for best stability.

Only now see what looks to be a Be Quiet lay cable lay out, think with 10 pins output and two cables coming out of that you'd be fine. Would pick a 10pin slot on the psu side that says it has it's own dedicated rail like the connectors with 12V3 and 12V4 next to it.

the other three pcie connectors seem to share rails.

@Vic 40
Not sure if I understood the 'rails' topic, I see it is referred to a lot with this PSU.

In this image http://bit.ly/05-psu-technical-data on the figure no 6 what exactly is 'a rail' ?
Is it the horizontal or vertical layout of the PCIe slots ?

About the recommended 12V3 and 12V4, why not 12V3 and 12V6 instead?
Why are there 12V5 labels and not just one?

Also on image 05, both tables have 2V5 and 2V6 in them. Is this a printing error?
Shouldn't it say 12V5 and 12V6 here since those are the markings we have on PSU ?

Thank you.

 

[Eximo]

Hello everyone and thank you for such a promptly answers

@Eximo
Sadly custom cables are not an option at the moment, so I will need to figure this out with the one's which came in the box.
So, if I understood correctly use two separate PCIe cables, plug one 6+2 part in one GPU slot, and leave other 6+2 part of one cable hanging, repeat the step with another PCIe cable, correct?

Yes

As for rails, that is an internal design of the PSU.

So you have a large AC to DC conversion that provides 12V, 5V, and 3.3V. On the 12V specifically, they will have made groups of wires that all share over voltage and over current protection, typically. So this means the maximum you can pull from each 'Rail' is limited by that.

Looks like they are labeled, just make sure your two GPU cables don't come from the same rail. Most are designed in such a way that each cable is on a rail by itself, however, sometimes the CPU shares a rail with some of the non-PCIe power connectors.

 

[Vic 40]

10 pin is P8 (EPS). PCI-e is 12 pin.

Yes , sorry my mistake, meant the right ones and circled those.

@Vic 40
Not sure if I understood the 'rails' topic, I see it is referred to a lot with this PSU.

In this image http://bit.ly/05-psu-technical-data on the figure no 6 what exactly is 'a rail' ?

Means that the power delivery is split into seperate "parts" as with bycoming features as explained by Eximo. The "parts" are called rails, most new psu's have one rail for the voltages needed, the +12V rail/ +5V rails / +3.3V rails /-12V rail, some pus's use multiple rails for the +12V rail.

About the recommended 12V3 and 12V4, why not 12V3 and 12V6 instead?

Because those connectors have their dedicate rails

Why are there 12V5 labels and not just one?

Don't know, but the connectors share rails. which i would not use if not having to.

Also on image 05, both tables have 2V5 and 2V6 in them. Is this a printing error?
Shouldn't it say 12V5 and 12V6 here since those are the markings we have on PSU ?

Thank you.

Yes probably print error and indeed need the 1 in front of them.

Think that you can do with just one pcie cable with it's two connectors looking at the pins (12) that provide the power and that the connectors on the gpu side arent'split of at the connector. The rails also provide 40A =480Watts which is enough for about every gpu.