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So I brought 2x Sapphire Vapore-X R9 280X video card. I am only doing 550kh/s each while on my other more powerful setup with the same card get about 750kh/s. I am wondering if the motherboard/cpu matters? Here is what I got on my new rig:

Asus P5K

Intel Core 2 Duo @ 2.66Ghz

2GB DDR2 Memory

As far as my research goes, this should all be fine, but at the end, the hash rate does not lie, what am I doing wrong?

  • are they all running the same configuration file? if so can you share the configs you are using? – Mark S. Dec 15 '13 at 5:57
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I highly doubt it. Even the PCI-e connectors do not really matter. I've got less CPU power and RAM than you and my rig is controlling 4x 7950s at full potential. The CPU/Motherboard is essentially calling functions. The functions themselves are what cost so much, and those are computed by the GPUs.

  • That is so weird then... thanks for the insight though. – Bill Dec 15 '13 at 1:28
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I Have seen comments that having less ram on your motherboard than in one of your GPUs can significantly reduce the hash rate. If your only running 2GB ram, but your cards have 3, so try 4GB ram on your mobo and see if that makes a diference

  • Looks like those GPUs each have 3 GB of ram does OP need to match and be running with 6 GB RAM for optimal performance? – Mark S. Dec 15 '13 at 5:56
  • I'll buy 2 more GB, RAM is cheap. But I don't know how much difference it will make. – Bill Dec 16 '13 at 15:38
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Only GPU matters. In the link you can see R9 series performance charts for LTC mining

http://www.youtube.com/watch?v=m_0j5ntR4w0

  • Wow, that's kind of impressive to overclock the 280x to about 980kh/h. To bad it doesn't say how that's done. – Bill Dec 16 '13 at 19:47
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From what i've gathered, the comments on matching system RAM only apply when your using Reaper as mining software. The likes of cgminer runs quite happily with only 2GB in system and 4 x 7950 3GB cards.

  • Make sure you are using TWO gpu threads, this is often the cause of underperforming 7950/7970/R9 280x – howardb Dec 16 '13 at 3:55

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