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by smoldesu 1198 days ago
That's... comically untrue. The Playstation 5 has faster memory than the M1 (448gb/s vs 200), and it was manufactured by AMD before Zen 3 or Apple Silicon even shipped. Dual-channel DDR5 should smoke the LPDDR4X in Apple Silicon in terms of memory bandwidth.
2 comments
sliken 1198 days ago
How so?

Memory bandwidth (peak, not stream)

  Ryzen 7950x =  84GB/sec #  128 bit wide ddr5-5200
  M1 =           66GB/sec #  128 bit wide ddr5-4800
  M2 =          100GB/sec #  128 bit wide ddr5-6400
  M1/M2 Pro =   200GB/sec #  256 bit wide
  M1/M2 Max =   400GB/sec #  512 bit wide
  M1 Ultra  =   800GB/sec # 1024 bit wide, m2 ultra not out
800GB/sec / 84 = 9.5. Although the ARM64 has a more relaxed memory ordering and generally you see a greater fraction of peak in the real world. Also Mac's default to a 16kb page, which helps the TLB with random workloads. Memory bandwidth is part of why the Apple iGPU does so well when compared to Intel and AMDs best iGPUs. Similarly the improved memory system is why the PS5 and XboxX does so well on games.

Sadly AMD is reserved the improved memory system for the XboxX and PS5. Both AMD and Intel limit laptops and normal desktops (except for the expensive HEDT segment like the Threadripper) to 128 wide memory.

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cjbprime 1198 days ago
The latest Intel/AMD non-HEDT memory controllers only have two channels, so your DDR5 would drop to below-DDR4 speeds if you put 128GB DDR5 in it.

(32GB dual rank sticks * 4 -- there are no 64GB DDR5 sticks yet. Some reports of system instability with all four DDR5 slots populated, too, even when running at DDR4 speeds, it seems the motherboard manufacturers aren't QAing it.)

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