GPU PCI-E connections

[CrippledROBOT]

Hello community! In discussion with an individual from tech support at Seasonic, I was informed that the most optimal way to power a high end GPU (GTX 1080ti) is to use two separate rails. In other words, do NOT use a single 8 +6 pin connector for your card, but use TWO (if that description makes sense). I attached a picture that he sent to me that describes this better.

 

What is your experience? Do you do this? 

[iRileyx]

It honestly doesn't matter if you use 1 or 2 rails to give power to the GPU. Unless each single rail isn't rated for the power the GPU needs(highly unlikely).

Lots of people only use single rail PSU's for high powered cards.

 

Though i remember watching a video from Jayztwocents, having each connector seperate on the PSU (like the first top photo) did give about a 2% performance gain. Not sure if they were on the same rail or not though.

[McHox]

well the official rating for 8 pins are 150w so it is understandable that a manufacturer goes with a guaranteed safe connection
however if your psu is on the better side it shouldnt be a big issue,might wanna touch the cable after a long gaming session to see how warm it gets tho

[ZyrtX]

I have always used a single rail and never had any issues (currently on 1080).

[CrippledROBOT]

3 minutes ago, RKRiley said:

It honestly doesn't matter if you use 1 or 2 rails to give power to the GPU. Unless each single rail isn't rated for the power the GPU needs(highly unlikely).

Lots of people only use single rail PSU's for high powered cards.

 

Though i remember watching a video from Jayztwocents, having each connector seperate on the PSU (like the first top photo) did give about a 2% performance gain. Not sure if they were on the same rail or not though.

That's what I thought too. I'm going to throw in my extra cable to see if that keeps the PSU a little cooler. 

[ZyrtX]

Just now, CrippledROBOT said:

That's what I thought too. I'm going to throw in my extra cable to see if that keeps the PSU a little cooler. 

Yea, I guess it's better for safety sake, if you have the option.

[Ashiella]

22 minutes ago, RKRiley said:

It honestly doesn't matter if you use 1 or 2 rails to give power to the GPU. Unless each single rail isn't rated for the power the GPU needs(highly unlikely).

Lots of people only use single rail PSU's for high powered cards.

 

Though i remember watching a video from Jayztwocents, having each connector seperate on the PSU (like the first top photo) did give about a 2% performance gain. Not sure if they were on the same rail or not though.

They were on different rails

[mariushm]

The term rail is incorrectly used here. In power supply terms, rails means a dedicated power supply output that has its own maximum current limits independent of the total power limit of the power supply .. for example a power supply could have two 12v rails, each with a current limit set at 20A of current, but in total the power supply may have a current limit of 30A  (less than 2 x 20A)

 

A video card is allowed to take up to 75w from a 6 pin connector  and 150w from a 8 pin connector, but there are sudden bursts and spikes which means through one connector the video card may pull up to 200w or even more for a few milliseconds.

 

When it comes to creating connection between power supply and video card you have to keep in mind how much electricity can each cable transfer in a safe way, and how much electricity a pair of connectors can pass between them without the connectors becoming damaged.

 

The connectors are rated for around 7-9A per pair  ( +12v and ground wires) so in theory a 8 pin connector can take in 3 circuits x 12v x 9A = 324 watts, so the connector itself will be fine even if the power supply takes a bit more.

How much current the wires carry depends on the thickness, and that is standardized.. power supplies use AWG18 or AWG16 cables.  The AWG 16 cables are thicker and in general can carry up to around 16-18A per circuit, and the AWG 18 cables can carry up to around 14-16A per circuit.

This is why it's possible to have one strand with two 8 pin connectors coming from the power supply, because the wires can carry more electricity than what the video cards are allowed to take from each connector.

 

However, the more electricity goes through a strand, the more losses are in that strand, in the wires. Also, the connectors are not perfect, there is some resistance between those connectors and heat is produced.

If you use two separate strands from the power supply to the video card, instead of a single strand with two connectors, you double the number of wires between the power supply and the video card, reducing the amount of energy that goes through each pair of wires, which also means there's less heat produced in the wires and you also put less strain on the connectors on the power supply.

 

The power lost in the cables (which is manifested as heat) also causes the voltage to drop slightly, let's say from 12v to 11.8v if you use two connectors on same strand. If you use two separate strands, the voltage drop could be lower, let's say only down to 11.9v ... and in some cases, this slightly higher voltage is enough to make the video card overclock 20-50 Mhz higher.

 

 

[CrippledROBOT]

2 minutes ago, mariushm said:

The term rail is incorrectly used here. In power supply terms, rails means a dedicated power supply output that has its own maximum current limits independent of the total power limit of the power supply .. for example a power supply could have two 12v rails, each with a current limit set at 20A of current, but in total the power supply may have a current limit of 30A  (less than 2 x 20A)

 

A video card is allowed to take up to 75w from a 6 pin connector  and 150w from a 8 pin connector, but there are sudden bursts and spikes which means through one connector the video card may pull up to 200w or even more for a few milliseconds.

 

When it comes to creating connection between power supply and video card you have to keep in mind how much electricity can each cable transfer in a safe way, and how much electricity a pair of connectors can pass between them without the connectors becoming damaged.

 

The connectors are rated for around 7-9A per pair  ( +12v and ground wires) so in theory a 8 pin connector can take in 3 circuits x 12v x 9A = 324 watts, so the connector itself will be fine even if the power supply takes a bit more.

How much current the wires carry depends on the thickness, and that is standardized.. power supplies use AWG18 or AWG16 cables.  The AWG 16 cables are thicker and in general can carry up to around 16-18A per circuit, and the AWG 18 cables can carry up to around 14-16A per circuit.

This is why it's possible to have one strand with two 8 pin connectors coming from the power supply, because the wires can carry more electricity than what the video cards are allowed to take from each connector.

 

However, the more electricity goes through a strand, the more losses are in that strand, in the wires. Also, the connectors are not perfect, there is some resistance between those connectors and heat is produced.

If you use two separate strands from the power supply to the video card, instead of a single strand with two connectors, you double the number of wires between the power supply and the video card, reducing the amount of energy that goes through each pair of wires, which also means there's less heat produced in the wires and you also put less strain on the connectors on the power supply.

 

The power lost in the cables (which is manifested as heat) also causes the voltage to drop slightly, let's say from 12v to 11.8v if you use two connectors on same strand. If you use two separate strands, the voltage drop could be lower, let's say only down to 11.9v ... and in some cases, this slightly higher voltage is enough to make the video card overclock 20-50 Mhz higher.

 

 

That is good information. I had an extremely minor smell coming from my PSU (if I put my face in the fan grill) that smelled like hot metal/hot plastic and was worried so I contacted Seasonic. They told me that loading that much stress on one line may be the issue. In the event that it is NOT, I just ordered ANOTHER of the same PSU. Maybe I just got a once in a lifetime bad Seasonic Platinum efficiency PSU. 

[McHox]

9 minutes ago, CUDA_Cores said:

*touches cable*

 

*gets shocked*

 

*dies*

well if your cables are bare copper you kinda deserve that shock kek

[Mat1926]

2 hours ago, mariushm said:

The term rail is incorrectly used here. In power supply terms, rails means a dedicated power supply output that has its own maximum current limits independent of the total power limit of the power supply .. for example a power supply could have two 12v rails, each with a current limit set at 20A of current, but in total the power supply may have a current limit of 30A  (less than 2 x 20A)

 

A video card is allowed to take up to 75w from a 6 pin connector  and 150w from a 8 pin connector, but there are sudden bursts and spikes which means through one connector the video card may pull up to 200w or even more for a few milliseconds.

 

When it comes to creating connection between power supply and video card you have to keep in mind how much electricity can each cable transfer in a safe way, and how much electricity a pair of connectors can pass between them without the connectors becoming damaged.

 

The connectors are rated for around 7-9A per pair  ( +12v and ground wires) so in theory a 8 pin connector can take in 3 circuits x 12v x 9A = 324 watts, so the connector itself will be fine even if the power supply takes a bit more.

How much current the wires carry depends on the thickness, and that is standardized.. power supplies use AWG18 or AWG16 cables.  The AWG 16 cables are thicker and in general can carry up to around 16-18A per circuit, and the AWG 18 cables can carry up to around 14-16A per circuit.

This is why it's possible to have one strand with two 8 pin connectors coming from the power supply, because the wires can carry more electricity than what the video cards are allowed to take from each connector.

 

However, the more electricity goes through a strand, the more losses are in that strand, in the wires. Also, the connectors are not perfect, there is some resistance between those connectors and heat is produced.

If you use two separate strands from the power supply to the video card, instead of a single strand with two connectors, you double the number of wires between the power supply and the video card, reducing the amount of energy that goes through each pair of wires, which also means there's less heat produced in the wires and you also put less strain on the connectors on the power supply.

 

The power lost in the cables (which is manifested as heat) also causes the voltage to drop slightly, let's say from 12v to 11.8v if you use two connectors on same strand. If you use two separate strands, the voltage drop could be lower, let's say only down to 11.9v ... and in some cases, this slightly higher voltage is enough to make the video card overclock 20-50 Mhz higher.

 

 

I really enjoyed reading your post...So basically if you are overclocking a single GPU, you might have better luck using two strands instead of one strand with 2 connector. In my case, it is only one 1080 Ti, and I use 2 strands although I am running @ stock speeds...