powered risers or not

[iarsenaux]

Ok i am running a mining rig with 3x r9 280x on a msi z87 g65 gaming edition motherboard but the temps are a bit high ( 78c, 88c, 90c) so i decided to buy some risers to make proper spacing between them. I bought 3pcs 16x to 16x pcie powered risers. Do i need to attach all molex to my psu ( 1250w zalman 80+ platinum) or can i just not use the molex?

[BitcoinEXpress]

Better stability if you use the molex adapters is the bottom line.

Less crashes, cooler riser temps.

The cards will source the power through the risers if you do not use the molex connectors.

I have done extensive testing on various cards with powered and unpowered risers over the past 3.5 years of mining.

~BCX~

[B737]

My PSU has only 1 cable with MOLEX connections. Can I use them for powering 2x 7950's or do I really need a second cable to distribute some load on that cable?

[iarsenaux]

Better stability if you use the molex adapters is the bottom line.

Less crashes, cooler riser temps.

The cards will source the power through the risers if you do not use the molex connectors.

I have done extensive testing on various cards with powered and unpowered risers over the past 3.5 years of mining.

~BCX~

thanks!

[Jamoke]

My PSU has only 1 cable with MOLEX connections. Can I use them for powering 2x 7950's or do I really need a second cable to distribute some load on that cable?

It's not really an issue of having 1 cable with molex or not, it's more an issue of how much voltage the rail has that is connected to your one cable.   If it's a 12v rail, then you probably would be fine to daisy chain 2 video cards off of the one cable, but it's most likely a 5v rail.  Usually this is printed on the side of the PSU.  If not, it definitely is in the instruction manual, or online.    ... 5v might be ok... but if you don't want to risk it, simply spend $150 and get a better PSU.  I wouldn't risk it, plus buying a better PSU, and riser cables opens you up to fitting more video cards if you ever need/want.

I had a lot of crashing problems running just 2 video cards on an old motherboard.   Using risers stabilized the voltage of both cards, and the motherboard, and now I no longer crash on that miner.   So overall I think powered risers are a must, so long as you have the case to mount an elevated video card.

[Damnsammit]

You should always use powered risers if you have the option.  You don't necessarily need them (but should still use them as a precaution) in the following situations:

1) You are only using 1 or 2 GPUs on a motherboard.  The motherboard should have no problem handling that without extra power.
2) You are using an Asrock BTC H81 Mobo or something similar that has additional power connectors directly on the motherboard.

[iarsenaux]

Weird. All the cards are working fine without the risers however the temps are very high. After i connected them to powered risers. On the first boot and attempt to run miner, cgminer crashed and blue screen appeared. I restarted it and it turned on but the 3rd GPU inserted on PCIE-7 16x is not showing up on device manager. I restarted the pc again and it won't boot up giving an LED code error 55 on my msi z87 g65 motherboard. i tried to use a different riser (1x to 16x) but card still can't be detected. Next thing i did is i moved it to the next slot which is PCIE-6 1x, same thing happened. it boot up, i opened device manager, there is a code 43, a lot of screen flickering then restarted and it won't boot up again code 55. finally i adjusted all slots, i am now using pcie 2(16x), 4(1x) and 5(16x) and they are all working properly. do you guys have any idea what happened to pcie slot 6 and 7 why it cant detect my GPU and why it crashes my pc?