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Title: Confused about PCI-E Extenders with Molex Connectors - Help Post by: Benny1985 on April 07, 2013, 04:21:47 AM I'm trying to figure this out, and help would be appreciated.
I'm in the process of fleshing out a rig that will use 5 or up to 6 GPUs (Radeon 7950s). Obviously, I need extenders for them, but I am totally confused as to if they need to be powered or not. At first glance, the GPUs should be powered directly by the PSU. If so, do I still need the PCI-E with Molex connectors? Or can I just use PCI-E extenders without the Molex connectors (which are significantly cheaper and easier to obtain)? I get conflicting information almost every time I ask. And for reference, I am planning to use the folllowing parts: http://cablesaurus.com/PCIe-x16-Extender-Cable-w-Molex-Connector GPU: http://www.newegg.com/Product/Product.aspx?Item=N82E16814202030 Mobo: http://www.newegg.com/Product/Product.aspx?Item=N82E16813130645 PSU: http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&DEPA=0&Order=BESTMATCH&N=100006676&isNodeId=1&Description=1250+watt+seasonic&x=0&y=0 Thank you! Title: Re: Confused about PCI-E Extenders with Molex Connectors - Help Post by: A Meteorite on April 07, 2013, 04:42:04 AM You will want the PCI-E extenders with molex if you hook up a lot of GPUs to a motherboard (greater than 4 if a good motherboard, or less if a junk one). The reason is they can pull 75W from the slot by spec (although cards usually pull most of their power from the PCI-E aux, you never know). I've seen pictures of melted ATX plugs/motherboards from too much current going over a few wires and traces.
If you want to hook up 5 or 6 7950s, you would definitely want at least 2 or 3 of them hooked up with extenders that have a molex. Also keep in mind you don't want to overload the molexes off your PSU. So try to use different chains... EDIT: Here's one such story. https://bitcointalk.org/index.php?topic=102890.0 I have seen others but don't have examples handy. Title: Re: Confused about PCI-E Extenders with Molex Connectors - Help Post by: MaGNeT on April 07, 2013, 08:26:07 AM DIY powered PCIe extender cables:
http://blog.zorinaq.com/?e=44 Title: Re: Confused about PCI-E Extenders with Molex Connectors - Help Post by: Benny1985 on April 07, 2013, 01:56:35 PM You will want the PCI-E extenders with molex if you hook up a lot of GPUs to a motherboard (greater than 4 if a good motherboard, or less if a junk one). The reason is they can pull 75W from the slot by spec (although cards usually pull most of their power from the PCI-E aux, you never know). I've seen pictures of melted ATX plugs/motherboards from too much current going over a few wires and traces. If you want to hook up 5 or 6 7950s, you would definitely want at least 2 or 3 of them hooked up with extenders that have a molex. Also keep in mind you don't want to overload the molexes off your PSU. So try to use different chains... EDIT: Here's one such story. https://bitcointalk.org/index.php?topic=102890.0 I have seen others but don't have examples handy. Could you explain this further: Quote Also keep in mind you don't want to overload the molexes off your PSU. So try to use different chains... How do I run them off different chains? Title: Re: Confused about PCI-E Extenders with Molex Connectors - Help Post by: A Meteorite on April 08, 2013, 04:17:31 AM Could you explain this further: Quote Also keep in mind you don't want to overload the molexes off your PSU. So try to use different chains... How do I run them off different chains? So you have a couple cables off the power supply providing a few molexes each. You shouldn't hook up every powered extender to the same cable coming out of the power supply. If I recall correctly, the max that you'd safely want to pull from a molex is 75W - exactly what the slot can provide by spec. So to be absolutely safe, try to use a different molex cable coming out of the PSU for each powered extender. However, if you must, I personally would feel safe with two on the same cable if it's a high quality PSU (but don't do it if you don't have to). |