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Author Topic: Quad GPU help, 2x5870 2x6870  (Read 1091 times)
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June 09, 2011, 04:13:03 AM

Hi all,

So I have windows 7 64 bit installed on a MSI GD70-890FX with 2 XFX 6870s and 2 5870s

For the lack of dummy plugs, I have connected each card to a monitor.. however only one monitor will actually display anything, the rest say check signal input.

When I power up the machine, only 2 cards are seen by the OS, one 5870 and one 6870

I have a 1000W power supply.

So my questions:
1) is it possible to run 4 of these cards in windows?
2) why are they not showing up?
3) should i attach a second power supply to some of the cards? The only other psu I have will not power on unless connected to a mobo.....
4) should i install a distro of linux? I havent found a way to OC the cards past 900 MHz in linux yet....

Thanks for the help Smiley
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June 09, 2011, 02:38:01 PM

You need to extend your desktop to the other cards.
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June 09, 2011, 04:28:03 PM

First of all I'd suggest making sure all the cards work, that means take out two cards, boot up with just the 5870s, see if it sees both.

Take out two cards, boot up with just the 6870s, see if it sees both.

If this works, it could well be that your PSU doesn't have a big enough 12V output and/or that it's not delivering 1000W constantly.

Each 5870 will use approx 190W of power, each 6870 will use approx 175W, this comes to a total of 730W before you take into account your system (I usually allow 150W for the system, unless there's anything really hungry in it).

A 1000W power supply (peak rating) may not be able to handle 880W consistent if it's not a particularly good PSU. Assuming all four cards work, your best bet is probably a bigger PSU or an extra PSU (probably more cash-viable but a bit more awkward).

As for Linux, totally recommend it if the machine is going to be a dedicated miner, purely because you can run without the GUI and squeeze a little more out of the GPU. It won't solve this problem though.

Hope this helps, and happy mining.

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June 10, 2011, 03:14:58 AM

Thanks for the replies...

After some investigation last night I am pretty sure that it is the powersupply...

I tried to reconfigure the power cables (its modular) to spread the drain over multiple connectors but that did not seem to help
1/4 of the time when I hit the power button the psu fan will spin a quarter turn, stop and the system wont boot.... pretty sure this is the issue  Cool

I have another older psu out of an old prebuild sony desktop that I tried to run one card off, but I could not get the psu to start without connecting to the mobo.. (tried shorting the green and black lines on the mobo connector). anyone else trying this?

Right now I have 3 of the cards mining, 2x5870 @ 435 MHash @ 75*C with fan on auto (usually around 45%) and the 6870 @ 315 Mhash @ 68*C fan also on auto...

Are those temps/speeds decent?

For those of you running linux, how do you OC the cards past 900 MHz? I would much prefer to run in linux but cant for the life of me OC my cards. the diff between 900 MHz and 980 MHz is about 75MHash for me...
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June 10, 2011, 06:29:46 AM

I've 1x6870 OC@1000 +/-78° fan on auto less then 50% (it keeps temp below 80°) 290 MH/s. It's an AUSUS with large heat pipe.

It works fine and it's very silent so I have ordered another one to add on same pc: a quality 650 PSU may be enough ??

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