Re:Memory access on the Apple M1 processor
by nkurz on Thursday January 07, 2021 @09:18AM
(#25671254)
The caching of the random[] array (almost) shouldn't matter, as the access is sequential.
I'm wondering if the difference is the the number of active memory channels. How many channels does your respective computers support? Do you have enough RAM installed so all channels are in use? Are you able to do a RAM bandwidth test by some other means to verify?
Another possibility is that for some reason the base latency is just different between your machines. A commenter added a pointer-chasing variation of Daniel's test on his blog. Maybe run this to find the full latency and see how the times differ?
Finally, there was one more commenter on the blog who reported anomalously fast times on a Windows laptop. It's possible there is a bug with Daniel's time measurements on windows.
I'm wondering if the difference is the the number of active memory channels. How many channels does your respective computers support? Do you have enough RAM installed so all channels are in use? Are you able to do a RAM bandwidth test by some other means to verify?
Another possibility is that for some reason the base latency is just different between your machines. A commenter added a pointer-chasing variation of Daniel's test on his blog. Maybe run this to find the full latency and see how the times differ?
Finally, there was one more commenter on the blog who reported anomalously fast times on a Windows laptop. It's possible there is a bug with Daniel's time measurements on windows.