Hash dropped after adding 3rd card

[vargoneti]

hello ,

i used 2 x 280x from sapphire ( 11221-02-40G vapor-x ) in my mining rig and was getting ~710 kh/s. I had another 280x (11221-00-20G) in my desktop , i was mining with it from time to time also and was also getting ~715 kh/s. After putting the 11221-00-20G into the mining rig besides the other 2 gpu , the hashrate dropped to around 670-680 kh/s no matter what settings i used. Could anybody help ?

The settings that i use atm and get around 680 kh/s are :

--thread-concurrency 8193 -g 2 -I 13 --temp-overheat 85 --temp-target 72 --expiry 1 --scan-time 1 --queue 0 --no-submit-stale --lookup-gap 2 --gpu-powertune 1 --worksize 256 --temp-cutoff 90

pls help

forgot to add , i have the 11221-02-40G undervolted to 1093 vdc , 1040 engine and 1500 mem clock
                                     11221-00-20G 1040 engine and 1500 mem , stock voltage

[crazyates]

hello ,

i used 2 x 280x from sapphire ( 11221-02-40G vapor-x ) in my mining rig and was getting ~710 kh/s. I had another 280x (11221-00-20G) in my desktop , i was mining with it from time to time also and was also getting ~715 kh/s. After putting the 11221-00-20G into the mining rig besides the other 2 gpu , the hashrate dropped to around 670-680 kh/s no matter what settings i used. Could anybody help ?

The settings that i use atm and get around 680 kh/s are :

--thread-concurrency 8193 -g 2 -I 13 --temp-overheat 85 --temp-target 72 --expiry 1 --scan-time 1 --queue 0 --no-submit-stale --lookup-gap 2 --gpu-powertune 1 --worksize 256 --temp-cutoff 90

pls help

forgot to add , i have the 11221-02-40G undervolted to 1093 vdc , 1040 engine and 1500 mem clock
                                     11221-00-20G 1040 engine and 1500 mem , stock voltage

Try these:

--thread-concurrency 8193 -g 2 -I 13 --expiry 30 --scan-time 15 --queue 0 --no-submit-stale --lookup-gap 2 --gpu-powertune 20 --worksize 256 --tgpu-fan 80

Make sure you don't use the 14.1 drivers, and don't open any other fan/temp monitoring software while you're mining. I noticed a 20khs drop when GPUz was open.