There exists cache friendly applications that see zero to minimal change with more bandwidth or more channels.
There also exists cache unfriendly applications that see large changes with more bandwidth or more channels.
Games generally are cache friendly, many easy benchmarks are cache friendly. But generally more aggressive use of a machine (which is presumably why you buy a top spec CPU) is generally less cache friendly. Also people notice worst case performance much more than average or best case. Audio skipping, user interface lag, etc.
You can see this effect in action when you compare single thread performance to multithead performance using every CPU. L1 caches are generally note shared, so if it's less than N times faster for N CPUs you are seeing software overhead (the cost of synchronization) or cache misses (in L1, L2, or L3) or of course main memory bottlenecks.
I've seen plenty of cases on older servers where running on all CPUs of single socket was FASTER than all CPUs of two sockets, but that's much less common these days because each socket has it's own memory system.
I can assure you that the entire server market and high end desktop market isn't running 2 to 8 time the memory bandwidth just for fun. The bandwidth is expensive and justified.
There also exists cache unfriendly applications that see large changes with more bandwidth or more channels.
Games generally are cache friendly, many easy benchmarks are cache friendly. But generally more aggressive use of a machine (which is presumably why you buy a top spec CPU) is generally less cache friendly. Also people notice worst case performance much more than average or best case. Audio skipping, user interface lag, etc.
You can see this effect in action when you compare single thread performance to multithead performance using every CPU. L1 caches are generally note shared, so if it's less than N times faster for N CPUs you are seeing software overhead (the cost of synchronization) or cache misses (in L1, L2, or L3) or of course main memory bottlenecks.
I've seen plenty of cases on older servers where running on all CPUs of single socket was FASTER than all CPUs of two sockets, but that's much less common these days because each socket has it's own memory system.
I can assure you that the entire server market and high end desktop market isn't running 2 to 8 time the memory bandwidth just for fun. The bandwidth is expensive and justified.