Why does this happen when cpu\GPU mining at same time?

[Ian Moone]

I have a 2p server with Opteron 6128s in it, when I try to mine with both CPU and my HD 7770 GPU the GPU drops from 180Mhash/s to 1.5Mjhash\s and can I fix this so That I can Mine with both at the same time?

[bitcoinsarefun]

I normally run minerd with 6 threads and it has no effect on my hashrate in cgminer. Raising it above that drops my hash rate considerably

i7-2600

[JennyHill]

Because you need to set the CPU affinity of each to use different cores. The CPU miner is cutting off the ability of the GPU miner to access the CPU and throttling it down. If you are running a Windoz machine: open the Task Manager – open the processes tab – search for the names of each of your miners and right click on them – change the affinity of each to a different core and the problem will go away.