Re:Memory access on the Apple M1 processor
by jeffbee on Wednesday January 06, 2021 @05:19PM
(#25663413)
If it works, it works. There will be no observable performance difference for DDR4 SDRAM implementations with the same timing parameters, regardless of the trace length. There are systems out there with 15cm of traces between the memory controller pins and the DRAM chips. The only thing you can say against them is they might consume more power driving that trace. But you wouldn't say they are meaningfully slower.
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Re:Memory access on the Apple M1 processor
by foldr on Wednesday January 06, 2021 @05:32PM
(#25663567)
You can't just eyeball the PCB layout for a GHz frequency circuit and say "yeah that would definitely work just the same if you moved that component 2mm in this direction". It's certainly possible to use longer trace lengths, but that may come with tradeoffs.
>The only thing you can say against them is they might consume more power driving that trace
Power consumption is really important in a laptop, and Apple clearly care deeply about minimising it.
For all we know for sure, moving the memory closer to the CPU may have been part of what's enabled Apple to run higher frequency memory with acceptable (to them) power draw.