Locking down the instruction set for virtualisation compatibility
With Shanghai, it's now possible to lock down the instruction set to a subset of the full complement. This feature is important in the live migration of virtual machines (VMs), using, for example, VMware's VMotion. If a VM is moved from one piece of hardware to another in a live environment, it could crash if certain instructions are suddenly no longer available.
If the instruction set is limited to SSE2 when starting a VM, then the VM can be moved to any server that uses at least a Pentium 4. Since Intel's newest processors — for example, the 6-core 'Dunnington' Xeon — also offer instruction set lock-down, it should now be possible to move VMs between live AMD and Intel systems — something that would have unthinkable until recently.
Of course, that instruction set lock-down means accepting the lowest common denominator. But in practice less than five percent of all standard software uses instructions outside SSE2, so a performance hit is unlikely.
The new Shanghai Opterons all consume 75W of Average CPU Power (ACP) — which corresponds to about 95W of Thermal Design Power (TDP) — and are available with clock speeds ranging from 2.3GHz to 2.7GHz. AMD will be releasing 55W models and a 105W chip running at 2.8GHz in the first quarter of 2009.
Prices for the CPUs for two-socket motherboards start at $377 for 2.3GHz, rising to $989 for 2.7GHz. The almost identical CPUs for four- and eight-socket boards are significantly more expensive: $1,165 for the 2.4GHz model and $2,149 for 2.7GHz.