Not sure about the amd side, but write combing was a big deal when the PPro core hit the scene. Basically was a large performance increase to have it enabled. Now with modern cards it seems a little hit and miss...
It helps transfers from a cpu to uncached memory. The problem is it caches transfers in a way that might be an issue ...holding them until there is a full 64 bits to write.
![[H]ard|Forum](/styles/hardforum/xenforo/logo_dark.png){kind=logo}