I have 3 different hosts for my VMs. On all VMs SEP 11 MR4 MP1a is installed.
the oldest host has older Intel CPUs without any hardware-assisted virtualization. I use MS Virtual Server 2005 R2 SP1 on this host, the CPU load of smc on the VMs (Windows XP, Windows Server 2003) is not good but ok (10%).
The second host has AMD Opteron 2.6 GHz CPUs whitch have AMD-V activated in BIOS. I use also MS Virtual Server 2005 R2 SP1. On the Vista VMs, smc use 50% CPU (saw tooth) as long as no user has logged on. If a user has logged on, smc use "only" 30% CPU.
If I disable the use of any hardware-assisted virtualization in the configuration of a VM, smc use "only" 20% CPU if no user has logged on. If a user has logged on to a VM, the CPU load of smc falls to lower than 10%.
My newest host has Intel CPUs, with hardware-assisted virtualization turned on in BIOS. I use Hyper-V in W2K8 x64. On all VMs (Vista, W2K3, XP W2K8, all 32 Bit) the CPU load of smc is lower than 10%. I made no tests with 64Bit VMs.
As I can see with my Hardware, SEP seems to have trouble with the AMD-V (hardware-assited virtualization) but not with Intel.
Perhaps someone can confirm this?