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Author Topic: Help figuring out how to set up 2 video cards  (Read 3418 times)
bustaballs
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June 20, 2011, 10:19:06 PM
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I've had a 6850 in my system before I learned of bitcoin. My new 6870 just came in.

I'm using GUIminer and it only recognizes both cards if they are crossfired. However, when I try to mine this way, it only gets about 230MH/s which is only 20 more than my 6850 alone got.

If I disable crossfire or take off the crossfire connector, GUIminer doesn't recognize the second card at all. What do I do? I feel like I should be getting well over 400MH/s now. Please help.

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InstaGx
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June 20, 2011, 10:54:24 PM
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I've had a 6850 in my system before I learned of bitcoin. My new 6870 just came in.

I'm using GUIminer and it only recognizes both cards if they are crossfired. However, when I try to mine this way, it only gets about 230MH/s which is only 20 more than my 6850 alone got.

If I disable crossfire or take off the crossfire connector, GUIminer doesn't recognize the second card at all. What do I do? I feel like I should be getting well over 400MH/s now. Please help.

I currently have the same problem with 2x 5770. My board doesn't support crossfire but they should work on their own.

Apparently you can try either a) changing something in your registry or b) connect another monitor or a DIY dummy plug.

I'm rather pessimistic about my case because I can't even find the second card in the device manager or anywhere else. The fan is active but that's about it. Maybe not enough power from the supply or something.

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bustaballs
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June 20, 2011, 10:57:56 PM
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Both of my cards are recognized in the device manager. This is a gaming computer so I can't use Linux. My board is Crossfire compatible.

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June 20, 2011, 10:58:22 PM
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Disconnect CF cable. Delete guiminer directory. Reboot.

Check both adapters now in device manager. Create guiminer directory again. Run guiminer. It should now see both cards.

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bustaballs
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June 20, 2011, 11:15:31 PM
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Just tried it. No luck.

bustaballs
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June 21, 2011, 12:44:03 AM
 #6

Oh ok. I got it. I set up a second monitor.

Do I need to leave the monitor in for it to continue mining? Also, where can I get these dummies? I don't see them on newegg.

InstaGx
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June 21, 2011, 08:23:24 AM
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Oh ok. I got it. I set up a second monitor.

Do I need to leave the monitor in for it to continue mining? Also, where can I get these dummies? I don't see them on newegg.

You'll most likely have to make the dummy plug yourself. One DVI-VGA adapter and 3 resistors. Doesn't look that hard to make in the link I posted earlier in this thread.

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tito13kfm
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June 22, 2011, 07:26:47 PM
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Oh ok. I got it. I set up a second monitor.

Do I need to leave the monitor in for it to continue mining? Also, where can I get these dummies? I don't see them on newegg.

You'll most likely have to make the dummy plug yourself. One DVI-VGA adapter and 3 resistors. Doesn't look that hard to make in the link I posted earlier in this thread.

Or no adapter and 1 resistor.

You only need to simulate load on 1 color.

InstaGx
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June 22, 2011, 07:29:53 PM
 #9

Oh ok. I got it. I set up a second monitor.

Do I need to leave the monitor in for it to continue mining? Also, where can I get these dummies? I don't see them on newegg.

You'll most likely have to make the dummy plug yourself. One DVI-VGA adapter and 3 resistors. Doesn't look that hard to make in the link I posted earlier in this thread.

Or no adapter and 1 resistor.

You only need to simulate load on 1 color.

I didn't try building a dummy plug myself but I heard that a DVI dummy is way more likely to destroy the card when done wrong. You're probably right though, 1 resistor should do the trick.

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tito13kfm
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June 22, 2011, 07:35:56 PM
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Oh ok. I got it. I set up a second monitor.

Do I need to leave the monitor in for it to continue mining? Also, where can I get these dummies? I don't see them on newegg.

You'll most likely have to make the dummy plug yourself. One DVI-VGA adapter and 3 resistors. Doesn't look that hard to make in the link I posted earlier in this thread.

Or no adapter and 1 resistor.

You only need to simulate load on 1 color.

I didn't try building a dummy plug myself but I heard that a DVI dummy is way more likely to destroy the card when done wrong. You're probably right though, 1 resistor should do the trick.

If you put it in the right holes it's really not possible to screw it up.  Anywhere from 50-150 ohm should work in theory.  I use 68ohm from radio shack.. 5 for $1.19  I know I could get them much much cheaper online, but I hate waiting 3 weeks for shipping on small parts.

yigga
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June 24, 2011, 01:04:45 AM
 #11

hey there...i'm facing almost the same problem. *bump*

have a hd5770 running on my mainboard (asrock k10n78FullHD-hSLI) in the pci-e x16 slot. (first monitor connected to this gpu DVI)

now i wanted to put another hd 5770 in the pci-e x1 slot (with a raiser 1x to 16x) but my win7 64bit wont recognise the second gpu. I have a tft connected to the second card as well with a VGA to DVI adapter.

What am I doing wrong? couldnt find anything. Or is it simply impossible to cennect an other gpu?

oh, and the second card doesnt show up in harwaremanager...and its not possible to enable second screen in diplay properties
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