Talk:Write combining

Computing Low‑importance

	This article is within the scope of WikiProject Computing, a collaborative effort to improve the coverage of computers, computing, and information technology on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.ComputingWikipedia:WikiProject ComputingTemplate:WikiProject ComputingComputing articles
Low	This article has been rated as Low-importance on the project's importance scale.
	This article is supported by Computer hardware task force (assessed as Low-importance).

Talk

This page is wrong when it says that write combining cannot be used for general memory access because of weak ordering.

It would be correct to say that naive write combining cannot be used, or that making write combining behave in a non-weak ordered fashion requires more complexity.

For example, the Intel P6 used write combining for ordinary WB memory in the special circumstance of "fast strings", REP MOVS and REP STOS. Or perhaps that is what the author would consider special purpose.

Another technique consistent with truly general purpose memory is what I call "left to right write combining": you combine so long as successive writes are exactly adjacent to and monotonically increasing within a cache line. If they are not "left to right", you evict the partial line. AMD's processors have had this for many years.

See http://semipublic.comp-arch.net/wiki/Write_combining#Left_to_right_write_combining

2600:1010:B024:ADA5:793D:DF5:D705:F191 (talk) 06:00, 6 November 2012 (UTC) Andy Glew[reply]