This is a bit old but it gives a basic outline. Worth reading the whole thing. It's short.
http://forums.amd.com/devblog/blogpost.cfm?catid=317&threadid=99513
I'll have a wild guess that it might also allow a larger number of VMs.
@ hoom
Virtualbox 3 has "experimental" 3D acceleration. It was a bit flaky when I tried it but I only slammed it on 32bit Win' 7 for a look.
http://forums.amd.com/devblog/blogpost.cfm?catid=317&threadid=99513
Why is it important?
In virtualization, there are lots of tricks done to abstract the underlying hardware, but also to minimize virtualization overhead. Using Rapid Virtualization Indexing(tm) instead of shadow page tables for memory management is only one example. The biggest remaining performance gap in today's virtualization scenario is I/O. An IOMMU helps to bridge this gap and also improves the situation from a security point of view. Last, but not least, it allows hypervisors to be simpler and more robust.
I'll have a wild guess that it might also allow a larger number of VMs.
@ hoom
Virtualbox 3 has "experimental" 3D acceleration. It was a bit flaky when I tried it but I only slammed it on 32bit Win' 7 for a look.