It’s really easy to accidentally UNDERPOWER your graphics card by using a split pigtail cable (also called y-splitter) for 2 or 3 of the PCIe connections on the GPU. Unfortunately a PCIe cable can supply as little as 150 watts from your PSU to the GPU, resulting in too low power being supplied to some graphics cards – especially ones with a TDP above 225W.
This isn’t an exact science, though, because the motherboard PCIe slot supplies 75 watts or so, and some PCIe cables/PSUs can supply MORE than 150 watts.
In general though, in this video I dive into exactly what you need to know here so that you can PROPERLY connect up – and power – your graphics card:
If you prefer text over video, please read on for the guide/transcript version of this video.
Video Transcript And Guide
Hey everyone, if you have a fairly powerful graphics card that requires two or even three PCIe connectors and you’re powering it with a SINGLE cable – by using these rubbish pigtail things – then you’re PROBABLY doing it wrong.
If you’re getting choppy graphics in gaming, or experiencing some crashes and freezing, it might be because you’re not supplying enough power to your graphics card. Some people would disagree with what I’m about to say in this video, but NVIDIA, Antec, SilverStone and others all say that you should be using SEPARATE PCIe cables for your graphics card. This is certainly true if your graphics card’s TDP – its rated power – is 225 watts or above.
Motherboard PCIe Slot
But why is this? Well let me back up a bit. Early graphics cards were fairly low powered, and simply plugging them in was enough. This is because the PCIe slot in your motherboard will supply around 75 watts of power. So lower powered graphics cards of old would be entirely powered by this 75 watts:
HOWEVER we now expect a LOT from our graphics cards, resulting in NVIDIA GPUs that are now bigger than a car:
Okay that’s a fake image, but in the last decade, graphics cards HAVE got much bigger and more powerful. This means that the paltry 75 watts from the motherboard PCIe slot is no longer sufficient, and so you need to run separate cables directly from your power supply unit to your graphics card to supply the extra power load.
Cable Gauge/AWG Limits
Here’s the issue. A cable can’t magically supply LOADS of power through it. It’s a bit like electrical cables (or “Romex” as you’d say in America) – the thicker the cable, the more power it can supply. This thinner cable is used for lower voltage deliveries like lighting circuits, while this thicker cable is used for wall sockets and things like that. If I wired up a wall socket with this thinner cable throughout my house, and then plugged LOADS of different appliances in, you could start to get issues with resistance and the cable heating up, and POTENTIALLY the cable could melt. Which is… bad.
Turning back to PCIe cables, it’s thankfully unlikely that you can wire up your graphics card so BADLY that the wires will melt – due to all the fail-safes and protections within your PSU, motherboard and graphics card. But if your graphics card needs two or three PCIe connectors, it IS entirely possible to supply an insufficient amount of power to your GPU, by just using a single PCIe cable and then relying on this weird pigtail connector to connect to the second PCIe slot on your graphics card:
This pigtail connector has a few names:
- Split end
I’ll call it pigtail from now on, but I wanted to mention the other names so that we’re all on the same page about this horrible, horrible connector.
Now, PCIe cables can officially supply up to 150 watts according to the spec. Sometimes it can be more than this, but let’s say it’s 150 watts for now. That means that if your graphics card needs MORE than 225 watts of power, using a single cable will NOT be enough for it – because the motherboard’s 75 watts and PCIe cable’s 150 watts is less than your card’s TDP. This will then result in poor gaming performance, or even crashes.
Run 2 Separate PCIe Cables
So what’s the solution? Well, it’s to run a SECOND, separate PCIe cable from your power supply unit. YES your PSU will probably only have a single rail for all the PCIe supply, but using a second cable means that you’re “freeing” yourself of the 150 watt restriction which exists because of the cable itself, not the PSU. In other words, the AWG – thickness – of the cable dictates how much power the cable can handle before resistance and heat becomes the “bottleneck”. By using a second cable, you’re then able to supply around 300 watts of power from your PSU to your GPU. PLUS you’re getting another 75 watts from the motherboard PCIe slot – allowing you to power cards up to 375 watts easily enough.
What About 3 PCIe Pin Cards?
This means that you can USUALLY power a 3 connector card like the RX 7900XT from just two separate cables:
After all, it has a TDP of 355 watts and so as long as you aren’t overclocking the card, you SHOULD be okay to use two cables and THEN rely on the horrible pigtail connector for the third PCIe connection. Yes I KNOW that I called this a “horrible, horrible” devilspawn connector and it KINDA is because it lulls people into a false sense of security, but in THIS case, it’s fairly useful. I guess. I still hate pigtail cables though (as you can probably tell!).
However if you purchased the Sapphire 7900XTX Nitro+, which is an overclocked card, two cables probably wouldn’t cut it because this has a TDP of 420 watts – meaning that 2 cables probably won’t be enough. You should THEN run three separate cables to it.
Notice how I said PROBABLY there? That’s because while I keep saying that a PCIe cable will supply 150 watts, many good quality cables and power supplies can supply more than this – potentially 288 watts or even 400 watts for the “best” AWG (gauge) cables:
That means that you might actually be able to power a 300 watt graphics card from a single PCIe cable just by relying on the devilspawn connector [cough] sorry, pigtail connector. Or, in the below example, a 263 watt card:
To be honest this all gets a bit confusing and unless you’re a qualified electrical tester with a bunch of testing gear, I would probably just prefer to err on the side of caution and always use two (or three) separate cables so that I can ensure the most stable power delivery to my graphics card possible .
Multiple PCIe Cables Are UGLY
The only downside of running multiple PCIe cables is that it looks UGLY. Just look at it!
Those unused pigtail connectors hang around the case and just mess up the aesthetics. You can’t easily hide the pigtail behind the motherboard tray either, because it’s only a few inches long so it just hangs around, unused looking ugly. Luckily there is a solution: single connector PCIe cables. Companies like CableMod and PSU makers like Corsair sell individual PCIe cables that only have one end on them:
These often come in pairs, meaning that you can plug these two separate cables into your PSU, and run each to your graphics card – and they end up looking a LOT nicer. I’m due to publish a video soon showing this in more detail, but these custom or “premium” PCIe cables are often individually sleeved too, allowing for a much neater finished look to your cable management inside your case.
PCIe v5 12 Pin Connectors
Before I wrap up, there is a “newer” type of PCIe cable for PCIe version 5 and this is known as the 12 pin connector. The way these work is that you have two separate PCIe “ends” that plug into the PSU, and then the cables are “merged” into a single connector which is plugged into your graphics card, delivering up to 600 watts IN THEORY. These cables have been a little controversial because SOME have melted:
Well, not “some” – there have been a LOT of reported cases of burnt connector ends. Putting that to one side, though, you should always aim to plug these high power, 12 pin connectors into two SEPARATE points on your power supply unit. Don’t use some weird connector that “merges” them back into a single PCIe point on your PSU – that will end badly, bad things will happen.
And that wraps up today’s video. I hope you found this video useful – if you did, please click the thumbs up button. While the YouTube algorithm is FAIRLY smart, it does also boil down to more likes equals more exposure. If you wanted to see more videos from me, then please also subscribe to me if you haven’t already – and thanks for watching!