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I'm running a miner with 4x 7950 cards. Right now it's using about 1230Watts/h and hashing 2,36 Mh/s
Running on the settings you see here below.

If anyone has a similar setup that runs less Watts then please advise me :)

"hotplug" : "5",
"kernel-path" : "/usr/local/bin",
"log" : "5",
"queue" : "1",
"scan-time" : "30",
"scrypt" : true,
"shares" : "0",
"gpu-threads" : "1",
"gpu-dyninterval" : "7",
"gpu-engine" : "1000,1000,1000,1000",
"gpu-fan" : "60-85,60-85,60-85,60-85",
"gpu-platform" : "0",
"gpu-memclock" : "1400,1400,1400,1400",
"gpu-memdiff" : "0",
"gpu-powertune" : "15,15,15,15",
"gpu-vddc" : "1.087",
"intensity" : "19,19,19,19",
"temp-target" : "78",
"temp-overheat" : "83",
"temp-cutoff" : "86",
"temp-hysteresis" : "3",
"vectors" : "1",
"worksize" : "256",
"lookup-gap" : "2",
"shaders" : "0",
"thread-concurrency" : "21712",
"no-pool-disable" : true

Veld   Waarde
Grafische Processor Eigenschappen   
Video kaart   AMD Radeon HD 7950 (Tahiti)
BIOS versie   015.031.000.000.000000
BIOS datum   24-1-2013
GPU Codenaam   Tahiti Pro
Onderdeelnummer   113-C3864000-100
PCI-apparaat   1002-679A / 1787-3000  (Rev 00)
Transistoren   4313 miljoen
Procestechnologie   28 nm
Verpakkingsoppervlak   365 mm2
Bus Type   PCI Express 3.0 x16 @ 2.0 x8
Geheugengrootte   3 GB
GPU Klok   1000 Mhz  (origineel: 930 MHz, overclock: 8%)
RAMDAC kloksnelheid   400 Mhz
Pixel Pipelines   32
Texture Mapping eenheden   112
Gecombineerde shaders   1792  (v5.1)
DirectX hardware ondersteuning   DirectX v11.1
PowerControl   15%
   
Geheugenbus-Eigenschappen   
Bus Type   GDDR5
Bus Breedte   384 bit
Werkelijke kloksnelheid   1400 Mhz (QDR)  (origineel: 1250 MHz, overclock: 12%)
Effectieve kloksnelheid   5600 Mhz
Bandbreedte   262.5 GB/s
   
Architecture   
Architecture   AMD GCN
Compute Units (CU)   28
SIMD Per Compute Unit   4
SIMD Width   16
SIMD Instruction Width   1
L1 Instruction Cache   32 KB per CU-Quad
L1 Vector Data Cache   16 KB per CU
L1 Scalar Data Cache   16 KB per CU-Quad
L2 Cache   768 KB
Local Data Share   64 KB
Global Data Share   64 KB
   
Theoretical Peak Performance   
Pixel vulsnelheid   32000 MPixel/s @ 1000 Mhz
Texel vulsnelheid   112000 MTexel/s @ 1000 Mhz
Single-Precision FLOPS   3584.0 GFLOPS @ 1000 Mhz
Double-Precision FLOPS   896.0 GFLOPS @ 1000 Mhz
24-bit Integer IOPS   3584.0 GIOPS @ 1000 Mhz
32-bit Integer IOPS   716.8 GIOPS @ 1000 Mhz
   
Percentage   
GPU   100%
Dedicated Memory   1406 MB
Dynamic Memory   58 MB
   
ATI PowerPlay (BIOS)   
State #1   GPU: 930 Mhz, Geheugen: 1250 Mhz  (Boot)
State #2   GPU: 930 Mhz, Geheugen: 1250 Mhz
State #3   GPU: 880 Mhz, Geheugen: 1250 Mhz  (UVD)
State #4   GPU: 300 Mhz, Geheugen: 150 Mhz
   
Frabrikant Grafische processor   
Firmanaam   Advanced Micro Devices, Inc.
Productinformatie   http://www.amd.com/us/products/desktop/graphics
Driver download   http://sites.amd.com/us/game/downloads
Driver Update   http://www.aida64.com/driver-updates

Undervolting is your friend. However, CGMiner can't actually set the voltage on those 7950 cards. You have to use a third party program like MSI AB, or tweak and flash the BIOS.

Use VBE7 (http://www.techpowerup.com/forums/threads/vbe7-vbios-editor-for-radeon-hd-7000-series-cards.189089/) to manually tweak the voltage, and then reflash your modified settings. HERE (http://www.cryptobadger.com/2013/10/undervolting-in-linux-via-modified-bios/) is a nice guide to follow.

I've got a 3.5Mh/s, 5x 280x rig that was pulling ~1450W, and I dropped the voltage to 1.019, and now it's pulling ~1250W. That's a 200W saving, which works out to 40W per card! Also does wonders for keeping the temps cooler as well.

Tnx I wil try this and post the difference when done.

Just finished up flashing my cards tp 1081Mv the rig went from 1230W to 1040W.
Right now i will tune the cards up again to and then try and lower some more probably.

Great way to spend the sunday afternoon  ;)

Great! Let us know how low you're able to get! Remember to let them mine for a solid ~20 minutes or so on each setting to guarantee stability.