You can check my Rig, I was able to run 4x 7990 @ 950/1500MHz 1.05V = TOTAL 1650W, or @ 900/1500MHz 1.025V = 1500W.
http://www.youtube.com/watch?v=MIuoLd8aaasMy Mining Monster Rig Review: http://[Suspicious link removed]/W7hGim
Cryptocoin Mining Profitability 2014: http://[Suspicious link removed]/lffJKq
Performance (depending on the clock/voltage):
CPU Usage: 55% (average)
RAM Usage: 1.9-2.2GB
Hash Rate: 4800-5600KH/s
Power Input: 1740-1970W
Power Output: 1500-1800W
Temperature: 58-79'C
Specifications:
Mobo: ASUS M5A99X EVO R2.0
CPU: AMD Sempron 145 (Single Core 2.8GHz)
Memory: Corsair Vengeance 8GB DDR3 1600
GFX: 4x MSI Radeon HD 7990 (8 GPUs)
PSU: Cooler Master Silent Pro M2 1500W
SSD: Kingston 60GB SSDNow V300
Cooling: Sinbo 18inch Floor Fan (75W)
Software:
Microsoft Windows 8.1 (64-bit)
AMD Catalyst 13.12
AMD APP SDK 2.9
CGMiner 3.7.2
Settings:
GPU Voltage: 1.050V (1.100V)
GPU Clock: 950MHz (1000MHz)
CGMiner 3.7.2: -l 13 -g 2 --thread-concurrency 8192
Windows 8.1 and 8GPU's
http://www.firstever.eu/wp-content/uploads/2014/01/5MH-Server.jpgMining Pool and 5MH/s+
http://www.firstever.eu/wp-content/uploads/2014/01/5MH-Pool.jpg