Advice needed for a custom PCIe power cable (Video added)

AlexTSG

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The final thing I need to get started with a long overdue upgrade of my old Alienware X51 R2 is a custom PCIe power cable.

The system allows for a graphics card drawing up to 170W, and has a custom low profile cable with 2x 6pin PCIe connectors. The clearance above the graphics card is a little over 10mm. To complicate matters further, both 6-pin PCIe connectors are wired into a single 6-pin connector on a DC-ATX board. The Alienware X51 R2 uses an external 330W Dell AC Adapter.

The graphics card I plan to install is a Radeon RX 5600 XT which has the same dimensions as the original Radeon R9 270, but uses a single 8-pin connector.

So, here are the problems:

  • I only have 10mm of clearance above the card for the power connector
  • I need to go from a 6-pin connector on the DC-ATX board to an 8-pin connector on the graphics card
  • The pin outs may not be standard
  • There is no space behind the graphics card to use a 180 degree connector (otherwise I could use a dual 6 pin to 8 pin adapter cable)
I would prefer to get a single sleeved cable which would need to be around 50cm in length, and have a standard height 6 pin connector on one side, and a very low profile 8 pin connector on the other.

This option from ModDIY looks like it would get me half way to a solution, although it would still be a tight fit:


But I would still need an appropriate 6 pin to 8-pin cable.

I see there are also these low profile 8 pin PCIe connectors, but that would require me to make up my own cable, something I haven't done before, and I'd prefer not to destroy a $300 GPU, or the whole DC board, or both!


I plan to strip down the Alienware tomorrow if I have time, so I can get an exact measurement of the existing cable, and do some continuity testing to see which pins go where.

I'll also shoot some video and/or photos of the connectors and clearances involved.

If anyone can recommend somewhere that would make up a custom cable (and tell me what info they would need), or point me towards somewhere where I could buy one, if it exists already, I'd appreciate it.

I'll update this post in the next day or so with some photos and/or video, as I realize this may all be a little difficult to envision from this post as it stands now.
 
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AlexTSG

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Here's a video to show how the PCIe power cable is routed in the system, with photos of the various GPU power connectors.



The cable is 45cm end to end including the connectors. I'll post pinouts next once I have figured them out with a continuity tester.
 

AlexTSG

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I used a continuity tester to check the pinouts. I have no idea if this follows any kind of standard, but this is the connector on the DC-ATX board.



If I follow the same numbering system for the PCIe connectors that attach to the graphics card, i.e. Clip at the top, counting the bottom row left to right, and then the top row left to right, then I get the following:

DC Board Pin 1 -> GPU Pin 4 (Ground)
DC Board Pin 2 -> GPU Pin 5 (Sense)
DC Board Pin 3 -> GPU Pin 6 (Ground)
DC Board Pin 4 -> GPU Pin 1 (+12V)
DC Board Pin 5 -> GPU Pin 2 (+12V)
DC Board Pin 6 -> GPU Pin 3 (+12V)

When connecting both PCIe power connectors to a dual 6 pin to 8 pin adapter cable, I get the following:

DC Board Pin 1 -> GPU Pins 4, 5, and 7
DC Board Pin 2 -> GPU Pins 6 and 8
DC Board Pin 3 -> GPU Pins 4, 5, and 7
DC Board Pin 4 -> GPU Pin 1
DC Board Pin 5 -> GPU Pin 2
DC Board Pin 6 -> GPU Pin 3

I did try connecting a single 6-pin connector into the left side of the 8-pin on the GPU, but it won't power up without Pin 4 and Pin 8 connected (Maybe just Pin 4 as that is marked as Sense B on diagrams I've seen).
 
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AlexTSG

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Looks like I have a solution thanks to Garett at Beyond Customs (https://beyondcustoms.net/). He's made up a custom 6-Pin to 8-Pin cable for me. I'll attach the low profile extension once I get that from ModDIY, and hopefully that will allow me to hook up the Radeon RX 5600 XT (or any other ~150W GPU that requires an 8-Pin PCI-E connector).

 

hopesparrow

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Jan 4, 2021
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Hi, were you able to finally have this cable installed and working with your setup?

I am currently trying to connect an 1080 to my Alienware and cannot for the life of me find the 6 pin to 2x6 pin cable for sale anywhere..
 

AlexTSG

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Hi, were you able to finally have this cable installed and working with your setup?

I am currently trying to connect an 1080 to my Alienware and cannot for the life of me find the 6 pin to 2x6 pin cable for sale anywhere..

According to my continuity tester, the cable from Beyond Customs is perfect.

Unfortunately, I'm still missing the 8-pin to low profile 8-pin extension cable that I need to get the graphics card working. I ordered it from ModDIY months ago, but they won't ship it during lockdown, and ours just keeps getting extended.

ModDIY have introduced a more expensive shipping option using DHL (which will ship), but that means spending $49 in shipping to get a $15 cable. However, if our lockdown doesn't end by mid January, which is the current end date, then I may just pay for the expensive shipping so I can actually get everything working.

I'll update this post in a few weeks once I know.

Damn this Coronavirus!!!
 

DrLeroy

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May 15, 2020
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I don't know how you feel about hard mods, but you can get those 8pin to dual 8pin adaptors and things online, I would look at getting something like this, and cutting the male connectors off and soldering them directly to the GPU so that the connector on the GPU is not a pigtail female, but I can understand such a thing is not for everyone though.
i.e one of these, cut off the males, solder wires to GPU where the socket is soldered on.
https://www.ebay.com.au/i/383884322...mjA2OFruQlPJ0rpqdJL1jgnYtyTxl1P4aAlCFEALw_wcB
 
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AlexTSG

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I don't know how you feel about hard mods, but you can get those 8pin to dual 8pin adaptors and things online, I would look at getting something like this, and cutting the male connectors off and soldering them directly to the GPU so that the connector on the GPU is not a pigtail female, but I can understand such a thing is not for everyone though.
i.e one of these, cut off the males, solder wires to GPU where the socket is soldered on.

I have a GutsParker dual 6-pin to 8-pin, which I've used to test the card outside of the case already.

The main reason I don't want to solder onto the graphics card, is that the Radeon RX 5600 XT I plan to use is an open cooler design, and the space in the Alienware X51 is extremely constrained, A blower type card is recommended.

If the card ends up not working out in there I want it to be easy to remove and use in another system.

As our lockdown has been extended yet again I've decided to contact ModDIY today and just pay the $49 in shipping to get the cables I need so I can get started with the project.

I'll probably take a few extra low profile bits and pieces for other stuff I have planned for my upcoming NCASE M1 build too.
 
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DrLeroy

Noob Saibot
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May 15, 2020
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I have a GutsParker dual 6-pin to 8-pin, which I've used to test the card outside of the case already.

The main reason I don't want to solder onto the graphics card, is that the Radeon RX 5600 XT I plan to use is an open cooler design, and the space in the Alienware X51 is extremely constrained, A blower type card is recommended.

If the card ends up not working out in there I want it to be easy to remove and use in another system.

As our lockdown has been extended yet again I've decided to contact ModDIY today and just pay the $49 in shipping to get the cables I need so I can get started with the project.

I'll probably take a few extra low profile bits and pieces for other stuff I have planned for my upcoming NCASE M1 build too.
can always solder the original connector bar on. . . its just solder. but I understand that's not for everyone, $49 in shipping is insane though, I would use individual bullet connectors for each wire before I paid that much in shipping for one cable.