Help with LTC rig: 3x5870

[monstrs]

Hello.

I have a problem to set up for LTC minig my rig.
I got there 3x 5870 cards. System is X2 255 processor, 6GB RAM, Corsair 850W PSU

When mining BTC, i can get ~ 440 from each card with ease
When i try to mine LTC with these settings:

cgminer --scrypt --worksize 256  --intensity 13 -o http://coinotron.com:8322 -u username -p password  -E 1

i can get only 290kh/s from each card, when clocked to 910/1300

Question is: How can i get more kh/s from those cards? I see that 5870 can get 400-440 kh/s. Thanks in advance.

[Ryu.Hayabusa]

5870 can definitely do 400-440, I average 425-430.
Try this: cgminer --scrypt -o http://coinotron.com:8322 -u username -p password --thread-concurrency 8000 -I17 -g1 --verbose
If your cards are the 2GB version then try 8000 first, then try increasing that to see if there is any performance gain.

I also recommend playing with the core/mem clocks as mine did not see an improvement past a certain point on both and in fact made hashing rates worse when I went higher.  There will be a sweet spot for the core/mem ratio, it'll just take time to find it.