Another discussion thread has noted that LPDDR4x can be 16x bits or 32x bits.
DDR4 is always 64-bits. Two channel DDR4 is 128-bits. So right there, 2-channel x 64bits DDR4 is the same bus-width as the 8-channel x 16bits LPDDR4x.
With that being said, 8-channel LPDDR4x is more than most I've heard of. But its not really that much more than DDR4 configurations.
128-bit (2-channel) DDR4 at 3200 MT/s is 51 GB/s bandwidth.
4266 MT/s x 128-bits (8-channel) LPDDR4x is 68GB/s. An advantage, but nothing insurmountable.
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A Threadripper can easily run 4-channel 3200 MT/s (100GB/s). Xeons are 6-channel. GPUs are 500GB/s to 800GB/s tier. Supercomputer-GPUs (A100) and Supercomputer-CPUs (A64Fx) are 1000+GB/s.
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HBM2 has a MINIMUM speed of 250GB/s (single stack, 1024-bits), and often is run in x4 configurations for 1000GB/s. That's what "high bandwidth" means today. Not this ~68GB/s tier Apple is bragging about, but instead HBM is about breaking the PB/s barrier in bandwidth.
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But yes, I'll agree that Apple's 68GB/s configuration is an incremental (but not substantial) upgrade over the typical 40GB/s to 50GB/s DDR4 stuff being used today.
I think I've read that there are now Ryzen laptops shipping with LPDDR4x as well. It's awesome that Apple is using ram with this much bandwidth, but it's not exclusive.
I completely forgot that 11th gen Intels actually supported LPDDR4 / LPDDR4x.
Its kind of ridiculous: LPDDR4 has been used in phones for years, but it took until this year before Intel / AMD added support for it. Ah well. This one is definitely on Intel / AMD's fault for being slow on the uptake.
DDR4 had largely the same power-draw of LPDDR3 (but was missing sleep-mode). So I think CPU makers got a bit lazy and felt like DDR4 was sufficient for the job. But LPDDR4x is leapfrogging ahead... the phone market is really seeing more innovation than the laptop / desktop market in some respects.
