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Comment by gumby | Hacker News Reader

Curious if you can feed all those Ampere CPUs or if it is memory bandwidth constrained.

Disclaimer: this is not a "zomg apple grate; others must suck" comment. Apple claims that their integrated design balances things out to get the best performance. It will be interesting once there are some real benchmarks to see how well that claim continues to stack up.

The M transition has been amazing, but not every iteration can be a winner.

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It has 8 x DDR4 3200, so about 204GB/s of memory bandwidth, 1/4th of the M2 Ultra.

Unless somethings dramatically changed with the M2, Apples chips can't leverage their full memory bandwidth in CPU-only workloads so comparing their numbers to those of a discrete CPU isn't especially meaningful. When Anandtech tested the "400GB/sec" M1 Max the most throughput they could coax out of it via the CPU was 224GB/sec.

https://www.anandtech.com/show/17024/apple-m1-max-performanc...

The huge bandwidth numbers on the M-series are mainly for the benefit of the GPU, less so the CPU.

Which means that M1 (previous gen) REAL numbers beat maximal theoretical numbers of ampere.

Sure, but that's a real number, not peak. The top ryzen (7950x) or top intel (i9-13k) manage only 83GB/sec peak, and something in around 60GB/sec real. Generally the arm memory model is looser than the x86-64, which allows a greater fraction of peak bandwidth. So apple chips that fit in thin laptops have 4x the memory bandwidth of the 150 watt and up high end desktops from Intel and AMD.

Sure the AMD Epyc (12 channel) or Intel Xeon (8 channel) compete, but at even higher power ratings and large physical sizes.

Not to mention that 224GB/sec leaves a fair bit of bandwidth for compression, matrix multiply, ML acceleration, GPU, video encode/decode, and related.

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