3 ms·

It's the chipset & CPU that have to slowdown to account for the extra cost to reach it, hidden in whatever stage you call it -- even if the actual DRAM chips ma

It's the chipset & CPU that have to slowdown to account for the extra cost to reach it, hidden in whatever stage you call it -- even if the actual DRAM chips may be the same. They're the dumbest part in this entire diagram. Also, they benefit from larger bus widths, lower power, etc. https://www.anandtech.com/show/16252/mac-mini-apple-m1-tested https://www.anandtech.com/show/16252/mac-mini-apple-m1-teste... ( despite this being DDR4 I have to go to DDR5-systems to find similar bandwidth & latency results ) , https://www.anandtech.com/show/17024/apple-m1-max-performance-review https://www.anandtech.com/show/17024/apple-m1-max-performanc... and https://www.anandtech.com/show/17024/apple-m1-max-performance-review/2 https://www.anandtech.com/show/17024/apple-m1-max-performanc... ( I have to go quad-channel DDR5 or HBM to find similar results elsewhere)

floatboth 5y ago
Time cost is dictated by the clock frequency and timings, not the physical distance itself. Lower distance may help with achieving better specs but Apple is not overclocking the memory, they run JEDEC spec. Maaaybe they train secondary and tertiary timings a little bit tighter, that’s about it. > despite this being DDR4 It is not! LPDDR IS NOT DDR!! It’s a very very different standard despite the similar name.
- AshamedCaptain 5y ago
  > It is not! LPDDR IS NOT DDR!! And is that what explains the apparent increase in memory bandwidth?
  - floatboth 5y ago
    Yes, LPDDR4X in particular is rated for 4266 Mbps (at least that's the only spec available from https://www.samsung.com/semiconductor/dram/lpddr4x/ https://www.samsung.com/semiconductor/dram/lpddr4x/ right now) while the top official JEDEC spec for DDR4 is 3200 Mbps. 4266 Mbps * 8 channels * 2 (bytes in a 16-bit channel) = 68.25GB/s theoretical maximum. (Or 4 channels * 4 bytes in a 32-bit channel, same deal.) See AIDA64 bandwidth benchmark results: https://storage-asset.msi.com/global/picture/news/2021/nb/lpddr-20210104-8.jpg https://storage-asset.msi.com/global/picture/news/2021/nb/lp... — these are from MSI's Intel Tigerlake laptops. There are AMD Renoir laptops with the same memory configuration too. This is not unique to Apple, this is what everyone has now. I guess the new big MBPs might have the largest version of this, but what the regular M1 has is not special whatsoever.

floatboth 5y ago

Time cost is dictated by the clock frequency and timings, not the physical distance itself. Lower distance may help with achieving better specs but Apple is not overclocking the memory, they run JEDEC spec. Maaaybe they train secondary and tertiary timings a little bit tighter, that’s about it. > despite this being DDR4 It is not! LPDDR IS NOT DDR!! It’s a very very different standard despite the similar name.

AshamedCaptain 5y ago
> It is not! LPDDR IS NOT DDR!! And is that what explains the apparent increase in memory bandwidth?
- floatboth 5y ago
  Yes, LPDDR4X in particular is rated for 4266 Mbps (at least that's the only spec available from https://www.samsung.com/semiconductor/dram/lpddr4x/ https://www.samsung.com/semiconductor/dram/lpddr4x/ right now) while the top official JEDEC spec for DDR4 is 3200 Mbps. 4266 Mbps * 8 channels * 2 (bytes in a 16-bit channel) = 68.25GB/s theoretical maximum. (Or 4 channels * 4 bytes in a 32-bit channel, same deal.) See AIDA64 bandwidth benchmark results: https://storage-asset.msi.com/global/picture/news/2021/nb/lpddr-20210104-8.jpg https://storage-asset.msi.com/global/picture/news/2021/nb/lp... — these are from MSI's Intel Tigerlake laptops. There are AMD Renoir laptops with the same memory configuration too. This is not unique to Apple, this is what everyone has now. I guess the new big MBPs might have the largest version of this, but what the regular M1 has is not special whatsoever.