Jeremy Likness' Blog

Windows 8: The Facts about ARM, Metro, and the Blue Stack

Many eyes will be focused on Barcelona on February 29, 2012 when Microsoft releases the Windows 8 Consumer Preview or what many are calling the beta version of the new platform. You’ve probably heard quite a bit about the Metro interface. It has design roots in Zune, Windows Media Center, and Windows Phone. It presents content-rich tiles and is designed to focus on a touch-first experience. Metro provides a unique experience and involves a specific set of tools and technologies. When you read that Internet Explorer 10 doesn’t support plug-ins, you aren’t getting the full story because it’s really only the Metro version that has this restriction.

Of course, we’ve just learned about the experience for Windows 8 on ARM machines. Probably the most revealing quote for me was this one:

“WOA will not support any type of virtualization or emulation approach, and will not enable existing x86/64 applications to be ported or run.”

There’s quite a bit that can be read into that statement, so let’s break it down for a second. Here’s what I understand:

1. Regular Desktop Applications will NOT run on ARM Machines

I never imagined this would be the case because ARM is simply a different architecture. Fundamentally, the instructions used by the CPU at the lower level are different instructions than the ones on x86 and x64 machines. Microsoft bridged the gap between x86 and x64 somewhat by introducing an emulation layer called WOW64 (Windows on Windows 64-Bit) that enables 32-bit (x86) code to run in the x64 environment. I speculated that a possibility might be that Microsoft would create a similar engine for ARM but that is clearly not the case. So all of those programs compiled to x86 and x64 simply won’t work.

It is possible that some applications may make it over. Microsoft was clear, for example, that they will provide special versions of Microsoft Office 15. This appears to be part of the “blue stack” or desktop mode for ARM, which raises some interesting questions. If I were to try to draw the architecture of the Windows 8 stack based on the latest announcement, it would look something like this. Keep in mind this is a typical “stack” diagram that is not a true architecture and there are some obvious issues (for example, Win32 technically extends beneath the Metro stack but I’ve kept it out to keep it simple). Here’s what I am picturing:


Notice that the entire Metro stack sits on top of the full suite of processors, while there is a definite dividing line between the x86 and x64 sides versus the ARM side. So What does it mean? Here is the first thing I can infer:

2. The .NET Framework will not target ARM devices

Notice there is no CLR layer in the blue stack side for ARM. From what I read I don’t think this is the case because if the framework were available, Microsoft would explain that a whole suite of existing applications should run fine. Ironically, one of the early points about the .NET Framework was that it contained an abstraction layer with MSIL (Microsoft Intermediate Language) that should allow it to target different platforms, including ARM. It doesn’t appear this effort was made. However, this does raise a point of confusion that I look forward to learning more about and clarifying as more information becomes available. Take a look here:


I know that on x86/64 machines, the C# version of Metro applications actually runs on the CLR. It uses the .NET Framework. There is a “core profile” that limits a number of Base Class Libraries (BCL) but it uses this nonetheless. There are also projections of the WinRT API that expose themselves as CLR objects. Since the announcement from Microsoft certainly embraced the fact that ARM realizes the full Metro stack, the implication is that this CLR layer exists. So the question is: do they have a version of the framework available? Did they just provide a smaller stub/trimmed down version like Silverlight that just supports the Metro stack needs? Is there a different mechanism altogether on the ARM platform that is something new? I’m sure these questions will be answered but it does make me curious. If we agree that there is not a general framework version available and we also know that there is no emulation/virtual layer, then I can also safely guess that …

3. .There is No Silverlight on ARM Devices

This is actually not something I’m disappointed about. It makes sense. The Silverlight runtime might not make sense for a number of reasons including the overhead of building a version that targets ARM (this has been done to support Windows Phone 7, but it is a different version) and battery/memory management concerns. I still think writing applications that target the platform specifically makes sense. There is a reason why iPad devices are so popular. They are fluid, the applications are responsive, and they just work. While an x86/x64 tablet has the perfect architecture to host the full desktop experience, ARM is a different architecture specifically targeting the mobile space and should be optimized that way.

This is why I’m fairly sure (and agree with the decision that) the ARM version of Metro won’t run plug-ins. The plug-ins are hosted on Windows machines and are therefore compiled to x86/x64 machine code which is not compatible with ARM. It simply doesn’t make sense for Microsoft to invest in building, what, a special ARM plug-in just for Silverlight?

However, there is a desktop experience and there will be applications released for this mode. So what makes me very curious is this:


So this is just my educated guess but from the post it is obvious there are desktop experiences like Explorer and applications like Office 15 that will target ARM. So what is the platform for building these? Will Microsoft make this available for us to use, so we can do blue-stack development on ARM machines, or will it only host some exclusive products? Is the engine they are using a C++ based engine or do they have a full suite of language options available that can target this area of the platform? Again, right now I can only speculate but it will be interesting to learn.

At this point you might wonder why I’m so calm saying Silverlight on ARM is a good choice when I just finished a book about Silverlight business applications. The answer is simple. Too many people assume that WinRT is the future for Microsoft and anything that isn’t supported by the Metro stack is going to become extinct. I disagree. In fact, I’ll say …

4. WinRT is NOT the Future for Microsoft

Don’t get me wrong. WinRT isn’t going away and is a major part of Microsoft’s future. I just meant it is not THE future for Microsoft. Contrary to speculation, Microsoft is not putting their eggs all in one basket and are not just focusing on Metro for Windows 8. I am still confident we’ll see traditional WPF and Silverlight development on existing Windows 7 machines and Windows 8 machines for the desktop side moving forward. Do you really think ALL complex user interfaces will go away? That certain people will stop doing CRUD data entry applications, or authors will suddenly be happy using the pen tool to write novels when they can type 15 times faster?

I doubt it.

There will still be a need for devices that run a powerful OS capable of building software and allowing us to use big Excel spreadsheets as well as pop open Word to write a document or PowerPoint to prepare a presentation. I don’t think that blue stack is going away any time soon. I also believe if you do find yourself doing Metro development, you’ll be using many of the same skills you are familiar with in Silverlight.

Don’t take my word for the fact that Windows 8 is not just about Metro. Let’s take a quick look at the evidence for the tale of two stacks.There has been plenty of talk about the jarring experience of falling back to the desktop mode. This mode is backwards compatible for applications that are written for previous versions of Windows and I’ve confirmed this by installing applications like Microsoft Office, Amazon Kindle, and several Silverlight-based touch applications including ones I’ve previously helped write. As my current book Designing Silverlight Business Applications goes into print, it’s comforting this paradigm is still fully supported on the new platform. So what is the evidence that the desktop mode is not just a mere fallback to Windows 7 that hides behind the Metro stack?

Here are a few announcements from Microsoft and changes with the desktop mode for x86/x64 targets that really stand out:

Fast Boot and Reduced Memory Footprint

Windows 8 boots fast. It’s not an illusion either. On an SSD machine you can shut down, press power for a cold boot and be working in your next application within seconds. This is a huge benefit – how many times have you actually delayed firing up your laptop because you dreaded the long boot time? That completely goes away with the new boot.Read about delivering fast boot times in Windows 8. Learn more about how these features also reduce the memory footprint.

Graphical UEFI Boot

The boot is not only faster. The boot supports the UEFI standard and is graphical. Remember those old text-based menus we used to have to navigate when dual-booting? Those are a thing of the past. Not only do you get a nice graphical boot interface, you also benefit from features like touch support so you can use your tablet to navigate the boot options. You can see screenshots of the experience and learn more about it in this link. This is not just an illusion, it works and it works with your Windows 7 applications.

Windows 8 on a Stick

This is a phenomenal feature that I haven’t seen covered much. It refers to the capability to install your Windows instance on a thumb drive so it can travel with you from work to home. This special version of the OS is capable of recognizing the device/hardware configuration and hosting the instance based on the environment you boot to. Imagine being able to install your favorite applications and configurations, then be able to take them and use them on your work desktop as easily as your personal laptop. You can learn more about this feature here.

New Explorer Experience and Features

The Windows Explorer experience has been completely revamped.While remaining familiar to users of the legacy version, it provides more functionality through the expanded ribbon interface. When you manipulate files from within Explorer, you will immediately experience the improved file management basics. Operations such as mounting VHD drives or ISO images have been completely integrated out of the box.The new concept of Storage Spaces allows you to organize pools of storage and virtual disks that behave like physical disks. Disk support has been extended to allow for larger disks with large sectors. This is a completely new file system experience that remains compatible with the legacy features you are familiar with.

Enhanced Task Manager

Microsoft took a new look at the task manager and completely refreshed its capabilities.This is substantial because it wasn’t just extended to support the new Metro platform. It now has a simple view for killing applications that does it quickly and efficiently. The grid was enhanced to help diagnose performance issues by providing heat maps and lighting up resource usage. It also groups like processes together.

There are actually many other features that address the non-Metro space for Windows 8 but I’ve gone on far enough in this post. I’m again very excited about Windows 8 on ARM and commend Microsoft for taking a non-compromise approach to making it the best experience possible. Although WinRT and the Metro platform is definitely the future for mobile and touch-based devices with Windows 8, I encourage you to keep pace with the desktop-based enhancements and remember there is an entirely different stack available for line of business applications that might not make sense in the Metro paradigm.

As a developer with XAML and C# skills you are well positioned to navigate both stacks as you build applications and have the freedom to choose what makes the most sense for your end user. Of course, I’m not assuming those are the only languages my readers know – and now there is a first class space for C++ development as well. No, I didn’t forget our HTML5 and JavaScript developers, but to be honest, that is the one block in the stack that I’ve spent the least amount of time in. I’m currently writing my next book on “Building Windows 8 Metro Applications with XAML and C#”. I believe there will be a huge benefit for existing Silverlight developers to work in both worlds. Look for more details from Addison-Wesley soon on that new title.

What are your thoughts about the recent announcements? Are you going to try to be first in line to download the next version when it becomes available?

On Feb 9 2012 10:33 AMBy jlikness Silverlight, windows 8With 1 Comment

Comments (1)

  1. "So the question is: do they have a version of the framework available?"

    Exactly. I take it you haven't looked at .NET development for WinRT yet? Core CLR functionality and language support appear identical but the BCL is quite different. It's not just that WPF and other desktop APIs were removed, quite a few core library features were stripped or redesigned as well. .NET for WinRT is not fully compatible with .NET 4 or 4.5 for desktop, most code is going to require some porting effort due to the different BCL.

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