https://www.purepc.pl/procesory/premiera_i_test_procesora_am...
A Broadwell with 3300 Mhz (3700 Mhz boost) beats a Kaby Lake (Skylake...) with 4200 Mhz (4500 Mhz boost)? Can the Broadwell use the 128MB EDRRAM from the iGPU as a L4 cache if the iGPU is not used? Would that actually make such a difference?
http://www.anandtech.com/show/10968/the-intel-core-i7-7700k-...
That's exactly what it does, and it gives you a "free"* ~20% increase in memory operations performance (which tends to be a ~20% increase in general performance).
* not actually free because you paid for those 128MB EDRRAM...
But from a consumer point of view, it increases performance (either for graphics or for the whole system if I have a discrete GPU), and it can also help with GPU numerical processing, because you get "free" transfers from memory (L4) to graphics memory by flipping a bit (or a few bits) in hardware. Don't know why this wasn't expanded further, appart from the cost of the embedded RAM.