Re: Is Intel exceptionally unsuccessful as an architecture

On 9/23/2024 2:00 PM, BGB-Alt wrote:

On 9/23/2024 3:39 PM, John Dallman wrote:

In article <20240923105336.0000119b@yahoo.com>, already5chosen@yahoo.com
(Michael S) wrote:
>

mitchalsup@aol.com (MitchAlsup1) wrote:

When only 1 x86 would fit on a die, it really did not mater
much. I was at AMD when they were designing their memory
model.

>

Why # of CPU cores on die is of particular importance?

>
Because multi-core made multi-processor systems commonplace, and far more
software started using multiple threads.
>

 Though...
 If one added a scheduling constraint that two threads within a single process could not run at the same time on multiple cores, with each process assigned an affinity to a specific core...

Affinity masks are nice, but iirc, they might be considered a sort of fairly "heavy" _hint_ to the underlying system, so to speak... In other words, it might not be 100% respected. Iirc I think I remember reading where a set affinity might not be held in 100% pure stone. Why does my mind go to Windows docs... ;^) It been a while. I remember as an older experiment I was pinning threads to cpus to try to get some sort of per cpu data in user space. I would day the thread local data on this pinned thread might as well be akin to per cpu data. What an experiment it was!

 Then memory consistency between cores would be less of an issue:
Threads would still behave as if there were TSO, on a weak-model CPU...
 

John