Clive Watson posted on his blog about the performance increase SLAT can give to Remote Desktop Services (the renamed and expanded Terminal Services) on Hyper-V running on Windows Server 2008 R2.
SLAT (Second-Level Address Translation) is available on the newest processors from Intel (EPT feature) and AMD (RVI feature) offer this functionality, e.g. Nehalem. It optimises memory management on Hyper-V, i.e. it offloads the mapping of physical to virtual memory to the CPU so that the parent partition is not involved. That reduces RAM overhead on heavily loaded hosts.
According to a quote that Clive posted for RDS virtual machines running on Hyper-V 2008 R2: “SLAT enabled processors increased the number of sessions by a factor of 1.6x to 2.5x compared to non-SLAT processors”. That’s a significant workload improvement.
I’ve been looking at pricing for new HP servers and components. At least when it comes to shelf prices the G6 chassis is more expensive but their processors are much cheaper than G5 ones.