user10031: 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?

user10850: 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

user10924: Only GPU matters. In the link you can see R9 series performance charts for LTC mining
http://www.youtube.com/watch?v=m_0j5ntR4w0

user10329: 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.

10031: <p>So I brought 2x <a href="http://www.sapphiretech.com/presentation/product/product_index.aspx?pid=2024&amp;lid=1" rel="nofollow">Sapphire Vapore-X R9 280X</a> 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:</p>

<p><a href="https://www.asus.com/Motherboards/P5K/" rel="nofollow">Asus P5K</a></p>

<p><a href="http://ark.intel.com/products/30784/" rel="nofollow">Intel Core 2 Duo @ 2.66Ghz</a></p>

<p>2GB DDR2 Memory</p>

<p>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?</p>
 10850: <p>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</p>
 10924: <p>Only GPU matters. In the link you can see R9 series performance charts for LTC mining</p>

<p><a href="http://www.youtube.com/watch?v=m_0j5ntR4w0" rel="nofollow">http://www.youtube.com/watch?v=m_0j5ntR4w0</a></p>
 10329: <p>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.</p>
