Question about video cards mining speeds

[deanorn]

Hello I'm pretty new to bitcoins so I'm hoping someone can help me.   Currently I'm using this Motherboard http://www.newegg.com/Product/Product.aspx?Item=N82E16813138318 with this processor http://www.newegg.com/Product/Product.aspx?Item=N82E16819103944.   I have a 5770 and a 4870 on it using a 630wpower supply.   Just mining with the 5770 I get a little over 200 mhash, just mining with the 4870 I get about 80 mhash.  But when I start mining with both at the same time the 5770 drops down to about 120 and the 4870 drops to about 40. 

Anyone know what could be causing this?

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[deanorn]

Don't think this would affect it but I am also using Wifi and not a wired connection for this pc.

[bcforum]

What software? What OS? What drivers? What SDK? Use the performance monitoring tools to see if your CPU is maxed out.

[deanorn]

Running Windows XP pro 32 bit, drivers 11.7.   Looking at the cpu it is pretty much maxed right now with just the 5770 running.  And I've tried using poclbm-GUI miner, and Cgminer.

[bcforum]

Try different driver versions. I think 11.3 is a good one.