I am using a slightly overclocked AMD 6850 and get around 270kh/s.
When running cgminer you need to set two environment variables. In windows I use a batch file with the following:
TIMEOUT 10
setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
cgminer
Timeout is just there so it waits 10 seconds to make sure MSI Afterburner has overclocked the cards before starting cgminer. It is available on Windows Vista and above and can be skipped by pressing a key.
You can create the batch file by entering this into notepad, click File > Save As and on the Save as type dropdown select All files. Choose a name for the file and make sure it ends with .bat then save it in your cgminer directory. You can run cgminer by opening this batch file or create a shortcut to it.
I am using a cgminer.conf file instead of command line arguments. If you are currently using command line arguments you can start cgminer, press S for settings then press W to write a config file. Press enter when it asks for the name and a cgminer.conf will be created. By default cgminer will use cgminer.conf if it is found in the same directory. You can have several configuration files and use them by supplying the --config or -c flag in the batch file e.g. cgminer -config dogecoin.conf or cgminer -c "C:\test.conf".
If you are using two different cards you will need to adjust the settings for each one by separating the values with commas. In the config below the 6850 settings are on the left, and the settings for my 7950 are on the right.
These settings work well for me but may need to be customised for your own use. In particular the high intensity in my config means the computer is unsuitable to work on while mining but will give slightly higher hashing rates.
{
"pools" : [
{
"url" : "http://pool-url:3333",
"user" : "username",
"pass" : "password"
},
{
"url" : "http://pool-url:3333",
"user" : "username",
"pass" : "password"
}
]
,
"intensity" : "18,20",
"vectors" : "1,1",
"worksize" : "256,256",
"kernel" : "scrypt,scrypt",
"lookup-gap" : "0,0",
"thread-concurrency" : "4800,21712",
"shaders" : "960,1792",
"gpu-engine" : "0-0,0-0",
"gpu-fan" : "100-100,100-100",
"gpu-memclock" : "0,0",
"gpu-memdiff" : "0,0",
"gpu-powertune" : "0,0",
"gpu-vddc" : "0.000,0.000",
"temp-cutoff" : "95,95",
"temp-overheat" : "90,90",
"temp-target" : "80,80",
"api-mcast-port" : "4028",
"api-port" : "4028",
"expiry" : "120",
"failover-only" : true,
"gpu-dyninterval" : "7",
"gpu-platform" : "0",
"gpu-threads" : "1",
"hotplug" : "5",
"log" : "5",
"no-pool-disable" : true,
"queue" : "1",
"scan-time" : "30",
"scrypt" : true,
"temp-hysteresis" : "3",
"shares" : "0",
"kernel-path" : "/usr/local/bin"
}
I am using cgminer 3.7.2 as that is the latest version with scrypt support.
These links might be helpful for configuring cgminer:
https://bitcointalk.org/index.php?topic=117221.0
http://www.brandonorndorff.com/bitcoin/mining/how-to-setup-and-optimize-your-cgminer-config-file/
