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My new graphics card (XFX RX 480 4GB) has one 8-pin power connector. I have Z600 workstation which has limited PSU connectors, one 6-pin connector and 1 additional rail that connects my hard disk and has additional Molex and SATA connector on that rail.

Problem

My computer has currently available one 6-pin connector and 1 Molex. The graphic card has one 8-pin connector only.

Reading forums in internet suggests not using only the 6-pin connector but also the additional 2-pin connector to get the full 150W from the 8 pins.

Math

The graphics card has 150 W power consumption, but users report varying power consumption at max usage between 120W to 220W (without OC).

PCI-e supplies the graphics card with 75 W

The 6-pin power connector carries the additional 75 W


Total of 150 W


Molex supplies additional 75W

Because my HDD is on the same rail, it will take away maximum of 25W


Total of 50 W from Molex.

6 pin + Molex = total of 200 W which is probably enough.

But because it might (very likely) exceeds the 150 W power consumption, I want to connect the additional 2 pins (the additional 50 W) as well.

There are two ways:

  • Molex to 2-pin (or Molex to 6+2 and use the 2-pin connector only)
  • Use 6-pin connector to 8-pin connector but sacrifice the additional power that it might needs.

The obvious option is the first one, but I haven't found a single adapter that suits me in my local stores (in about 100 km range). That means I have to wait additional one month to receive my items from online store (eBay has everything) if I bought them from there.

Any other options? I might found some other connectors/adapters from my local stores.

After some more research...

Someone from this post which asks about the safety of converting 6 pin to 8 pin wrote a comment saying that he went to a professional guy and asked if that's safe to do and he confirmed it.

That's one of the options currently but this way the graphics card isn't supplied with all the possible power that it might need.

A 8-pin connector can supply up to 150W which will be good (-25W used by my hard drive).

After spending more time in the internet...

How does this sound like:

 Molex -> Molex to 6-pin -┐
                          ├--> 2x 6-pin to 8-pin
 6-pin -------------------┘

S O L V E D

I got the cable today and I have been playing GTA V for 2 hours now at maximum settings and it hasn't shutdown nor throttled (still the advertised clock speed).

Conclusion: Yes, XFX RX 480 4GB can run with 6-pin power connector instead of 8-pin (with 6-pin to 8-pin adapter).

Thanks for everyone who helped to get this case solved!

  • 3
    What is the wattage on your power supply anyway? – Smock Aug 7 at 15:11
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    dectrader.com/pdf/quickspecs/13277_na/13277_na.html Looks like a 650W 80Plus PSU which is above the minimum for that specific card but the 2 missing pin will sacrifice the performance of the graphics card. – CaldeiraG Aug 7 at 15:20
  • @CaldeiraG Thank you, good to know. I haven't found that information anywhere until now. – YoungDev Aug 7 at 15:55
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    Just to remark that 6- and 8-pins both have only three 12V pins, and both can carry much more than the rated 75W and 150W measures which were made with old-style PSUs. If one is to believe the official numbers that are being thrown around, even an 8-pin wouldn't be able to run a high-end GPU, not to mention do bitcoin mining. – harrymc Aug 7 at 16:25
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    I would rather stick to the 6pin->8pin adapter and underclock a little bit if needed but statistics show that it should stay around 150W so I hope I don't have to do that. The price was just so good that I wouldn't find anything else that good for that price. Also I'd like to enjoy my graphics card before the summer ends and schools starts, because returning and buying new one takes 2-3 months. Thanks for the help tho. – YoungDev Aug 8 at 11:20
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Don't just try and plug 6pin into 8pin socket on it's own.

Could you not get a 6pin -> 8 pin converter like this one?
A lot of PSU's have 6+2 cables which is essentially what the above does

Or 2x molex to 8pin PCI-E like this one?
(Although I'm skeptical on this one)

mixing the 6pin plug with a molex->2pin (is that even a thing?) also sounds dodgy to me

What is the wattage of your PSU anyway - are you sure it can handle the draw consistently?

I've always either matched PSU to MoBo+Cpu+GFX or made sure that it has cables that are compatible with either (2x 6+2 for instance), but then I have a thing for modular PSUs

  • I have been thinking if 6 pin -> 8 pin is enough as it doesn't offer more power than a full 8 pin connector will. Also I only have 1 molex cable available in the system. – YoungDev Aug 7 at 15:58
  • Mixing 6+2 pin sounds weird to me as well but it sounds like it should work :D Take a look at the comment on my question, CaldeiraG wrote a comment showing the specs of my PSU. It's 650W so it shouldn't be a problem in this case. Also my power supply isn't replacable. – YoungDev Aug 7 at 15:59
  • Ah sorry, I missed that you have a HP Z600 somehow (even though it's in the first line). We have a couple of Z640's here, they're quite beefy. – Smock Aug 7 at 16:17
  • But what do you think of that option that is at the bottom of my question (the "After spending more time in the internet...")? – YoungDev Aug 7 at 16:48
  • I've got to be honest, at this point I'd be wondering if I could return the graphics cards under distance selling regulations (if they apply where you are) and looking for one that actually fits with the rest of the hardware. – Smock Aug 8 at 8:16
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PCI-e supplies the graphics card with 75 W

The 6 pin power connector carries the additional 75 W

Total of 150 W

Afaik, there is no guarantee that a PCIE card will always use the maximum allowed from the slot, it could just grab more or everything from the PCIE power cable instead. There have even been cases where graphics cards don't follow the spec and go over the power limit of both slot and power cables.

I know this is not the answer you want to hear, but I would personally not mess around with the power limits of the Molex cable or the 75 Watt limit of the 6 pin. Get a new power supply if it is standard ATX. A good quality PSU is not expensive nowadays and really not something to skimp on.

  • I can't change the power supply, its special made for this workstation, it's HUGE. I can't fit anything else in it. – YoungDev Aug 7 at 15:57

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