Unfortunately we have found that AMD-based servers can run much slower than the equivelent Intel. I would recommend making the "usual" changes (as mentioned in http://community.qlik.com/docs/DOC-2362) but it will always be slower than if you'd stuck with Intel.
Ahhh yes, the described issue on bad performance using AMD CPU has been approved by Qliktech officially. Up to then we reduce the number of CPU in BIOS to 8. We're now waiting for a new software release. This has been announced w/o certain date.