PCI Express X1 to x16 risers - powered or not

[Takeshi_Kovacs]

I am considering the purchase of some X1 to X16 riser cables as I add GPUs to my (modest) setup.

I can easily obtain un-powered units and I wonder if I need powered units or not.

Does anyone have experience in this matter?

Is it feasible to take a non powered cable and solder on a molex line with a 12V connection? The powered units that I see on sale only seem to have the 12V line and no 0V return.

Has anyone tried this? How did it work out?

[talexeh]

Since a rig isn't exactly cheap, I rather take the safe path & get myself powered riser cables. There's a certain risk of burning the connector if you're using unpowered PCI-e riser cable.

[icebear888]

I have tried to use unpowered cables ( I didnt know powered ones existed!) and it didnt work in my setup.

I probably know why now

[Damme]

Hello!

I just bought 1x -> 16x risers, no power

the power input seams very simple, looking at http://pinouts.ru/Slots/pci_express_pinout.shtml

pin 1B, 2BA, 3A is +12v
pin 4BA is ground
looking at pictures there is one capacitor 16v 1000µf (I do not belive its true, too small on the items I've looked (ebay) lol!)
Anyone owning and can take hi-res pic? I'm thinking of modifying mine before I use them.

Edit:
I see some connectors ONLY use +12, no gnd, no cap.

Edit again: mixed A+B - Corrected now!

Jet another edit:

http://en.wikipedia.org/wiki/PCI_Express#Pinout
+12 : 1B, 2BA, 3BA
gnd : 4BA

[TheUnk]

What card are you trying on the X1?

I have a 7970 on a non-powered x1 to x16 working no problem for a few weeks now, but the 7970s have 2 power plugs so maybe it does not pull much from the slot

[jmbinfo]

I have a HK connection if anyone needs these pM me.

[Takeshi_Kovacs]

What card are you trying on the X1?

I have a 7970 on a non-powered x1 to x16 working no problem for a few weeks now, but the 7970s have 2 power plugs so maybe it does not pull much from the slot

I have not tried anything at the moment. I have a 7850 on a machine all by itself and I was considering moving that to another machine that has a 7970 already and a spare X1 slot.

Perhaps I could try it with my 7970 on the X1 slot.

[FTLAUDMAN]

When I'm using 4 7950s per rig I find that I can usually get away with only having 2 of the 4 risers be powered. That said, I've decided to get powered risers from now on. Why skimp on the cheapest part in the system?

I've been having good success with these 1x to 16x risers - http://www.ebay.com/itm/261216266308?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

[oxxon]

I have one riser without molex power, but with an 7850, i think, that the molex is requiered for more power cards, like 7970, etc

[Takeshi_Kovacs]

Thanks for all the comments guys.

I have ordered a couple of unpowered risers and, when they arrive, I will try them as they are and consider having a go at soldering a molex on for power.

I will report back when I see what happens. It will be a while as I am in NZ and it takes ages to get stuff here by mail order and lots of suppliers are reluctant to send stuff here.

[sdminer]

powered would be better. they will draw power straight from power supply vs going through the CPU with nonpowered ones. electronically makes sense

[splnkr]

I'm working on this too. Just waiting on my molex connectors. I tried adding a 3rd 7970 to a mining rig with an unpowered riser and it didn't work. Yes, for most motherboards you'll need powered risers for anything more than two high-hashrate GPUs.

PCIe 16x GPUs can individually consume up to 75w directly through the motherboard. What's happening when these attempts fail is that the GPUs are trying to get more wattage from the motherboard than it can provide.

You can estimate the total PCIe wattage supported by your motherboard by adding together the spec'ed power for each actual PCIe slot you have (16x, 8x, etc.). The info for all widths is here:

http://en.wikipedia.org/wiki/PCI_Express#Power

[GR1P]

Ive had good luck running cheap China-made Ebay un powered risers with 3 7950s and a gigabyte ud3 mobo.

Adding a 4th card though......

[nails]

i sell both powered and non powered and when people ask for suggestions i always tell them 4 or more power 3 and under you should be fine with non powered. if you cant get the extender to work then you have a motherboard with a hot swapable 1x port and you need to bridge 2 pins so the motherboard recognizes the x16 card as they arent set up quite the same as a 1x device. alot of motherboards also have problems using 1x to 16 risers on x16 slots. ive sold these on ebay and and never had a customer email me with a problem after i give them that advice. you can make powered out of non powered and if you do i would attach both the + and - to the molex as current flows from the - to the + so just having + on the molex isnt really doing anything but bringing the current into the psu after it goes threw the gpu. Still drawing power threw the motherboard.

[captainbluff]

I'm using 3 unpowered  PCIe risers ( 2 16xto16x and 1 16x to 1x ). No problem so far, all our Gigabyte 7950s

[sabd]

How much are they out of interest?

I have a HK connection if anyone needs these pM me.

[Hephaestus]

I've got rigs with 7870 XTs and 7950s (six per board), and I use three powered and three unpowered risers on each (all x1 to x16, even on x16 slots, doesn't make a difference).  I don't add extra grounds, I just cut the +12V wires and attach a molex.  You've got nine grounds on the PCIe x1 connector, and then all the grounds on the PCIe power connectors - you don't really need more.

[nails]

powered would be better. they will draw power straight from power supply vs going through the CPU with nonpowered ones. electronically makes sense

the power doesnt get drawn threw your cpu.

[nails]

How much are they out of interest?

I have a HK connection if anyone needs these pM me.

everyone has a HK connection its called ebay they are 3.2 with shipping if you want to wait 3 weeks to get it

[jrblevin]

Is it feasible to take a non powered cable and solder on a molex line with a 12V connection? ...

Has anyone tried this? How did it work out?

I made two powered cables following this guide and they work perfectly:

https://bitcointalk.org/index.php?topic=76121.0