Here’s an interesting article on XP Mode hardware virtualization requirement

I don’t care too much for the title, and would put a bit of my YMTC (you make the call) to it, but nevertheless, this article brings out some key facts about hardware vitualization that i think you should know about and will find interesting.

Microsoft, Intel goof up Windows 7's "XP Mode" (ars technica)

So right off the top I would take some issue with his statement in the subtitle: “…But now we learn that Microsoft and Intel have contrived to make XPM unavailable to many Intel users.”   I consider that an unwarranted negative spin, so let me throw a little YMTC on this.  Well, I don’t know about you, but after what we know about the “Windows Capable” debacle, I’ll be really surprised if we find out that MS did, in fact, conspire with Intel to “limit XPM availability to many Intel users”, just to help Intel upsell some CPUs.  in fact, Jon (the blog author) makes the point at the very end that he isn’t sure why Microsoft is requiring VT support for XP Mode -- so, I guess it’s OK for him to make up his own reason, thus, I take issue that his subtitle and article imply it’s a marketing conspiracy - YMTC.  But in that vein, I don’t know myself (yet), but I’m thinking that it’s more likely that VT is required for the updated version of VPC not just for the XP VM, and that this is less about a marketing conspiracy and more about Microsoft’s platform virtualization strategy for desktop virtualization.

Here’s some other points of interest (IMHO) in the article…

“The vast majority of AMD's lineup, except for Sempron, has AMD-V and will work”.  But, from Jon’s point of view, the fact that Intel doesn’t include VT on many of its procs should apparently dictate that MS not require it for XPM.  The fact that Intel segments their procs around Intel-VT, for marketing (revenue) purposes, is too bad IMHO.  In fact, Jon characterizes it as a “boneheaded move on Intel's part” (to not include VT on more or all CPUs).  But to imply that MS has goofed up XPM for requiring VT, again without more specific knowledge of what the decision was based on, is indicative of the bias (and “small picture” perspectives) that I see so often in the blogosphere.  (And why I do these YMTC bits from time to time.  Of course, some might claim that I have my own bias <grin>.)

One interesting technical piece of information he shares is that “Intel's VT-x and AMD's AMD-V work by introducing a set of instructions that make x86 fully virtualizable without the use of binary translation.”  This is a great nutshell definition of what the hardware virtualization technology does. Jon goes on to say that “VT is the way to go if you're rolling out a new x86-based virtualization package, like Microsoft's hyper-V.”   But, he then states that XPM is a binary translation solution (which I’ll assume is true), so as alluded to above he wonders “why did Microsoft mandate VT support for XPM”.  Well, even though a reason may not be obvious, I can only say that in my 11+ years at MS, I have found that there is ALWAYS a reason for why things are done in our software the way they are, and I have to say that from the times when I’ve been privy to the decision process, that invariably, if you were presented with the same set of decision criterion (or if you had the same kind of “big picture” view), you would make the same decision.  Perhaps some more information will come to light about “why VT” in future whitepapers or engineering blogs.

In the meantime, it is important for all our partners to understand that XPM does have the Intel VT/AMD-V requirement, for whatever reason, and that there are a significant number of Intel CPUs that do not have it, including some fairly recent ones.  Ed Bott has a list of the supporting CPUs on his blog.

On a related note, I find it almost amusing that many of the posts and articles I’ve seen around this subject whine about the fact that the Atom processor doesn’t have VT --  like one would want to use a 1-2gb RAM netbook to host VMs.  I guess they have to find fault with something.

In closing, I would also remind you that XPM is a stand-alone (unmanaged) solution (vs some of the enterprise focused virtualiztion solutions such as MED-B and VDI) and intended for the small business space, thus it is slated to be available in the Professional (and higher) versions of Windows 7.