Topic: PCI Express risers? (Read 2415 times)

Good advice, thanks. I guess the next step would be to power then externally as many have done. First of all I would need 1 or 2 additional PCI Express 3 "extension" cables (is any such animal available?) running from wherever the GPU's are housed (male one end, female the other) going to the additional 2 slots on the mobo (there are 3). My power supply (600w) only has 2 connectors for the GPU's, so even if I did re-do one of the other cables coming from it to power a third (and external) GPU, I wonder if the total amp/watt rating would be enough to handle 3 of them. I could get another PS to power the external GPU's as well.

One of my temporary rigs was my gaming machine. 2 R9 280x's, built in a HAF X case, 2 slots apart, with the side panel open, and fans blowing in very cool air (25-35*F) from the outside ducted directly to the GPU intakes -- still overheated the top card. That's even undervolted to .980v VDDC. Unless I bring the ambient temp in the room down to about 60*F or so, the intensity will regularly drop to cool down the GPU. On the coldest nights <32*F, the cold air was enough to keep the GPU temp steady @ ~74*C. The room, which isn't particularly small, with a fan blowing in air from the outside, self regulated to about 62*F ambient when I had both cards running, but I started having low humidity problems in the house because of the dry air constantly pumping in. Waking up feeling like a dried out sponge with a nosebleed isn't fun. 

The heat output on these cards is enormous. Build it into a larger case, use risers, and/or use a skeleton frame case if you want to run multiple GPUs of this class. These aren't 7950's, they will heat you out.

no 2 cards needs a full ATX case and oonly 2 or 3 cases could fit them side by side

Just a quick question, while I'm on this thread.. I'm building a new rig using an ASRock Z77 Extreme 3 mobo and a mid-tower with a Intel Core i3-3220 Ivy Bridge 3.3GHz LGA 1155 55W Dual-Core Desktop Processor and a 600 watt power supply for scrypt mining of Litecoins using a Radeon R9 280X GPU in Linux. Do you think a second card of the same type will be able to be added inside the case (physically fit side-by-side?) using the provided SATA3 slots and work/cool correctly?

I dont think im capable of installing  "pipes". Maybe yellowpages have a "pipe" installer. Does this apply if i was just to use 16x to 16x risers?

What?  Amp draw is not pushed.  You can't "feed back" power into the motherboard in the fashion you're implying, provided your powered riser has a ground connection as well.  This "feed back" will only occur with shit cables that only use a +12v input, and no ground.  I have no idea how robust the mobo's grounding circuit is, so I don't know if it can handle the load, but better safe than sorry.

OP, think about it this way...

Each copper trace/wire is a different sized flexible pipe, that will only flow a limited amount of water (electricity/amps).  The more pipes you have going to and from the device (video card).  When your device needs more water than the pips can supply, it strains the system.  Like trying to suck a milkshake up a standard plastic straw.  When there's too much power draw, this pipe will start to flex, and eventually it'll collapse (like when a chunk of cookie gets stuck in the milkshake straw's bottom).

To solve this, you simple use more pipes (6/8-pin PCIe power connectors to video card, powered risers, etc.), or larger pipes (thicker ga wiring).

The pipes(copper traces) on your mobo cannot be changed, and are meant to supply 2, maybe 3 high draw devices maximum.  So to sufficiently power multiple GPUs, prevent motherboard burnout, and keep everything happy, you should install more "pipes."

Don't thank him. That reply is loaded with incorrect information.

Thank you vm1990

true but both options contain that risk if you draw to much power from the line youll burn out the motherboard but if you use to many powerd raisers they feed back into the motherboard and fry it. its why its good to use a combanation of powerd and unpowerd so the unpowerd ones take any extra amps away from the board the powerd ones get the juice they need and the board only has to find a small fraction of power for the gpus which makes everything happy

This discussion has been had a few times. https://bitcointalk.org/index.php?topic=199706.20

Not having powered risers is a risk that only you can decide if you want to take. 

I don't know how many power lines are on a 16x slot, but it appears as if there's only 1 powered pin on all PCI-2 slots, which is where the power wire is attached in the risers.  If this is the case, most boards will support 2 card easily, with higher quality boards (advertised as supporting 3-way SLI or Crossfire) being able to support 3 unpowered.

Once you go above this, then powered risers are almost a must IMO.  Some have successfully utilized unpowered risers, but you risk burning out your motherboard.

I know powered risers are hard to find right now, but I may have some available.  See related subforum.

Okay thanks again

MUST is a strong statement.  Also inaccurate.  A decent board will run 3 GPUs no problems without powered risers.

pretty much yes but make sure you have atleast 1 in the regular x16 slot that is unpowerd that way your not going to fry the motherboard as easy

Thanks guys for the replies, so if im using 1x to 16x then i use powered. Got it

more or less yes good motherboard makers and good boards all handle different some you can use powered but basically if theres a pci x16 slot use unpowerd for them and if you have to use x1 slots use powered risers... that way the motherboard is able to balance the extra loads a bit better.

^^^^^^^^^^
||||||||||||||||||

is the correct answer. I'd add that if you are going to put in 3 or more GPU's on one motherboard, you MUST use powered risers. If you are going to put in 1 or 2 GPU's on one board, I'd use a plain riser (without power).

That is not how that works. The cards pull this "juice" you speak of. Using a powered riser does not make your psu have a greater output. If you have a signle rail 12v psu, you can pull all the juice you need from the motherboard via the atx connection....until it melts.

The reason a lot of people use the powered risers is to bypas the power coming in to the 12v on the gpu via the socket, which can cause some damage to the board. Also, with multiple cards, you have more of a draw at the 12v pins on the motherboard from the power supply (anything yellow really). These components are often not made to run with 4 or 5 cards. They expect 2 at most is many cases. This means that 5x cards may be to much for what your board is spec'ed at. 


The powered design does more than just move the card away from the board and its neighbor, but puts 12v power right to the pins on the pcie lane of the card. Some gpu makers have made adapters that will take up a lane on your motherboard, that allows for 12v power injection into the board for increased performance. This sort of feature would not only take away from your pcie real estate, but still have large amounts of 12v travelling over the pcie bus.

In my experience it is a good idea, if nothing else it lets you put more cards on a single board since heat dissipation is severely better with spaced out cards.  Plus the last thing you want is to have a handful of cards and you can't run them since non-powered risers don't give enough juice.   Worth the $8-$10 you might pay right now since I'm assuming you are mining scrypt and prices are pretty darned good at the present.

I was wondering if it was best to get powered risers (1x to 16x) or not. Could someone please advise.
thanks