SLAT is a capability present in both Intel and AMD processors that allows the processor to handle the mapping of the physical memory to virtual memory for virtual machines (VMs) taking a workload from the processor. For Windows Server 2008 R2 SP1, SLAT is required on the server if the RemoteFX role service is enabled, because it’s a huge benefit when dealing with graphically intensive operations.
For Windows 8 Client, most systems will be expected to have some high-end graphical capability (certainly compared to servers), and because of these higher-end graphics, SLAT is required on the processor if Hyper-V is to be used.
For Windows 8 Server, SLAT isn’t required unless the RemoteFX role service is enabled, in which case SLAT is required, as it is with Windows Server 2008 R2 SP1.
Essentially, if your hardware runs Windows Server 2008 or Windows Server 2008 R2 Hyper-V, then it will run Windows Server 8 Hyper-V with the same features.