8+4 EPS: Last 4 pins of PCI-E cable fit, but is it safe?

viivo

[H]ard|Gawd
Joined
Sep 7, 2005
Messages
1,680
I don't know if my PSU(HX1000i) came with two 4+4 cables and I lost one or it was always just one, but until now I haven't needed both. I found that four pins on a pcie cable fit perfectly in the 4-pin connector, but is it safe to use?

It's irrelevant whether or not the extra EPS connector is necessary - it's one of the last things on my troubleshooting list and I just want to know if this cable would work.

20200510_192138.jpg


20200510_192954.jpg
 

GiGaBiTe

[H]ard|Gawd
Joined
Apr 26, 2013
Messages
1,199
No, it's not safe to use, EPS12v and PCIe have inverse polarity. Thankfully most motherboards have idiot proofing to not start if PCIe plugs are used on the motherboard, else you'd have a smoldering crater when you turned the system on.

spsgx-png.png

Whoever decided to use the same keying on both EPS12v and PCIe power must have been smoking some strong shit.
 

viivo

[H]ard|Gawd
Joined
Sep 7, 2005
Messages
1,680
Thanks. EPS is standardized then? Any ATX-EPS cable on, say Amazon, will work?
 

Starfalcon

Limp Gawd
Joined
Jan 7, 2020
Messages
243
Well again it depends on the keying at the PSU side, as most PSU makers also use their own keying that isnt compatable with other PSUs.
 

mda

[H]ard|Gawd
Joined
Mar 23, 2011
Messages
1,851
What CPU/Board do you have? You LIKELY can run with just the 4 PIN.

Take note that you only really need the 8 PIN (4+4). The extra 4 PIN is mostly just for show unless you are a hardcore overclocker.
 

GiGaBiTe

[H]ard|Gawd
Joined
Apr 26, 2013
Messages
1,199
Thanks. EPS is standardized then? Any ATX-EPS cable on, say Amazon, will work?
EPS12V is a server power standard. The connector on the device (motherboard) is standardized, but not on the power supply itself. You can't rely on generic Amazon cables because every manufacturer has a different wiring pinout for modular cables. If you need extra cables, you should contact the manufacturer of your power supply and see if they'll sell you what you need. If that's not possible, I'd just get a new power supply that has the cables you need. There is of course the DIY route of making custom cables, but you need to be absolutely sure you know what you're doing, or you can end up with a smoldering crater at worst, or something that doesn't work at best.

What CPU/Board do you have? You LIKELY can run with just the 4 PIN.
Two 18 AWG wires (the gauge the ATX12V standard specifies) can do about 380 watts full tilt, not that you'd ever want to do that. The benefit of using a full 8 pin EPS12V connector is that the load is spread across more pins. I've seen several instances where the connector is the weak link and has resulted in burned/melted connectors. And with Intel not really being honest about the TDP of their CPUs since the Core 2 era, it's best to be safer than not. Many of their modern CPUs can pull orders of magnitude more power than the TDP rating, especially when using HT and some instruction sets like AVX.

Take note that you only really need the 8 PIN (4+4). The extra 4 PIN is mostly just for show unless you are a hardcore overclocker.
It can also improve safety margins of the connectors by having less current flowing through them.
 
Top