[Sanmayce]

Just looked at:
http://ark.intel.com/

Sandy Bridge-E:
Processor Number: i7-3930K
# of Cores: 6
# of Threads: 12
Clock Speed: 3.2 GHz
Max Turbo Frequency: 3.8 GHz
Intel Smart Cache: 12 MB
Lithography: 32nm
# of Memory Channels: 4
Max Memory Bandwidth: 51.2 GB/s

Sandy Bridge-E:
Processor Number: i7-3820
# of Cores: 4
# of Threads: 8
Clock Speed: 3.6 GHz
Max Turbo Frequency: 3.8 GHz
Intel Smart Cache: 10 MB
Lithography: 32 nm
# of Memory Channels: 4
Max Memory Bandwidth: 51.2 GB/s

Gulftown:
Processor Number: i7-980X
# of Cores: 6
# of Threads: 12
Clock Speed: 3.33 GHz
Max Turbo Frequency: 3.6 GHz
Intel Smart Cache: 12 MB
Lithography: 32 nm
# of Memory Channels: 3
Max Memory Bandwidth: 25.6 GB/s

Sandy Bridge:
Processor Number: i7-2700K
# of Cores: 4
# of Threads: 8
Clock Speed: 3.5 GHz
Max Turbo Frequency: 3.9 GHz
Intel Smart Cache: 8 MB
Lithography: 32 nm
# of Memory Channels: 2
Max Memory Bandwidth: 21 GB/s

Looking on Max Memory Bandwidths (51.2 GB/s vs 25.6 GB/s) one cannot ask oneself how Intel doubled the performance by adding 4 channels vs 3 channels, meaning it should be 6 channels if dummy math is done.