|
|
|
|
|
|
by jabl
2401 days ago
|
|
|
> The downsides of MESI are that (a) it requires broadcasts No, it can be implemented with directory instead, e.g. https://en.wikipedia.org/wiki/Directory-based_cache_coherenc... Or various combinations of snooping and directories ("snoop filters", or directories that act as "bridges" between broadcast domains, etc.). In current Xeon processors (and presumably AMD EPYC as well, thought I don't yet have first-hand experience with those), you have a couple of directories per CPU with snoop filtering, as with tens of cores broadcasting becomes a scalability bottleneck. In the BIOS you can change the mode how it operates, with slightly different names and semantics depending on the CPU generation. |
|
|