PCIe riser cables question.

[Jonathan Lemmens]

For my new PC in a custom case, I need to use a PCIe riser cable, I got 3 of these from my dad's office server (It came with the server but he doesn't use them).

 

All three of them work fine with an old GT 9800 even when OCd and testing with Furmark. There seems to be no difference between using the molex connector and not. But I'm a bit hesitant to use this in my main rig as I've heard risers like this quite often fail and may damage the GPU. 

 

What is the extra molex plug used for? Would it be better to use this without the molex plugged in and is using these riser cables really that risky?

The capacitor on there is a solid state Nichicon capacitor, can I therefore assume this riser cable is a "quality component"?

 

I will be using this on a Asus ROG Strix Z270 ITX mobo with an XFX R9 380X, but i'll probably be upgrading the GPU later this year.

 

 

[TheRandomness]

The cable will be fine. The power cable is there to supplement the 12V rail that comes from the PCIe slot, but the distance may cause some voltage drop/loss of quality, so it's there to alleviate those issues. 

[Pokemoneuro]

It doesn't seem like the molex connector is meant to be there... Like, if it's from a server maybe it's been modified to have a molex connector added. I guess that if you use the riser and not connect the molex to anything it'll work just fine

[Misanthrope]

I am unsure if the server motherboard provides the 75 watts of power for pcie 16x slots by default and if it does not that's what the molex would be for. Your consumer motherboard does provide power over the pci-e 16x slot.

 

I know consumer riser cables do not have this molex though but I am unsure if this is the intended purpose.

[Bcat00]

Server wire means reliability comes first. The molex is there to ensure power doesnt suddenly drop and cause a sudden blackout on the card because of the extended wire.

 

Use the molex if you want and i would because it just simply means a extra safety measure.

[Jonathan Lemmens]

11 minutes ago, TheRandomness said:

The cable will be fine. The power cable is there to supplement the 12V rail that comes from the PCIe slot, but the distance may cause some voltage drop/loss of quality, so it's there to alleviate those issues. 

That makes a lot of sense actually, that's probably why that capacitor is there too. 

 

1 minute ago, Bcat00 said:

Server wire means reliability comes first. The molex is there to ensure power doesnt suddenly drop and cause a sudden blackout on the card because of the extended wire.

 

Use the molex if you want and i would because it just simply means a extra safety measure.

So does this

 

Thanks guys. I may test it again with a GTX 470 I have, just to be sure. But at least I'm a lot more confident now.

[Narnash]

These extra molex slot is meant to deliver 12V normaly provided from the PCIe slot itself. These modified risers become very popular through the mining boom were people pluged as many GPUs in a motherboard as possible. The mainboards even though they're designed to deliver some power through the slot (depending on "length" x1 25W, x4 25W?, x8 50W?, x16 75W) are not really meant to deliver that much current on all the slots leading in dead or burning motherboard traces.

The mining people modded molex connectors for extra power by themself to prevent motherboard damage. Than some day the chinese manufacturers get that risers with extra power already installed could raise sales and today you can find risers with this extra molex connector as easy as one without one often at the same price.

 

 

PS: You can use this extra connector (as long it's properly soldered) or you don't. It really doesn't matter as long you don't dasy-chain more than 1 riser or use super long ones (higher electrical resistance the longer the cable is)