Microsoft's cavalry is on the offensive, with Windows 8 and Ultrabooks on track to challenge Steve Jobs' post-PC legacy.
Microsoft might have won the war with Apple for PC market-share years ago, but there's no question that Apple's dominance in this so-called post-PC era, when the centre of computing shifts from the PC/notebook to the tablet, smartphone and cloud has led many to claim the Wintel era is coming to a close.
Not only is Apple's iPad the tablet that consumers want, beating competitors on price, form factor and desirability, it is quickly becoming obvious that it is cruelling sales of new PCs and notebooks too, as people figure out they can get work done on an iPad alone.
Even while Android eats away at iPhone sales, Apple still has unchallenged supremacy in the tablet market, with 74% market share. All notebook sales have been stalling at 4% growth rate per year, while tablet sales have been growing 178% per year.
It's easy to see why the analysts have been writing off Microsoft. The company is tied to what look like sunsetting products: the declining PC, a big traditional OS which has not made a successful transition to tablets, and big, expensive Office apps at a time when software is becoming far more affordable and easily purchased through app stores. Its move into mobiles, with Windows Phone 7 and the deal with Nokia, is yet to bear any fruit. Worst of all, in the fast-growing tablet space, Microsoft is nowhere, giving Google a free pass to second place in the market with Android.
Microsoft and Intel, both of whom have found themselves in the uncomfortable situation of having a very weak product offering in tablets, are desperate to stem this tide towards the iPad or 'post-PC' era.
Microsoft's magic 8 ball
Microsoft's solution to the problem it sees brewing in the computer industry is Windows 8 - a dramatically reinvented version of Windows that is designed to be equally at home on a low-power tablet, a netbook, an ultrabook, a corporate notebook or a desktop PC.
While Windows 7 was about remedying the shuddering train wreck that was Vista (and perhaps should have been provided free to people who suffered through Vista), Windows 8 is a ground-up reinvention of what Windows is, and it's absolutely clear that making touch interfaces part of every PC is Microsoft's number one priority.
Windows chief Steven Sinofsky is candid about the fact that Microsoft hasn't done much to the front-end of the operating system for 15 years, commenting that consumer expectations today are "a lot different than in '95 - the last time Windows underwent a significant and bold overhaul."
The new Windows gets a completely new touch-oriented interface called "Metro", taking styling cues from Windows Phone 7. It ditches the Start Menu and Desktop metaphor, uses live-updating tiles rather than icons, and uses multi-touch to allow users to swipe and zoom through screens of the interface.
The traditional Windows interface is still available with a tap of the Window key, but Microsoft is offering some big carrots to developers to make apps for Metro, rather than developing old-style Windows software.
For a start, apps that run in the Metro interface will work without any modification on low-power, ARM-based PCs, and only Metro apps will appear in Microsoft's own app store, the Microsoft Store, which will be preinstalled into every copy of Windows 8, which Microsoft is pitching to developers as a shopfront with a potential 400 million instant customers.
As is always the way in the tech industry, once there's something better, Microsoft isn't ashamed to slag off what it was promoting as state of the art last year.
About Windows' legacy codebase, Steven Sinofsky told developers: "It's extremely rich, and it's extremely riddled with … feedback from you on how these parts don't exactly always work well together."
Secondly, developers who don't jump enthusiastically into Microsoft's new world of the touch interface will be left behind. Sinofsky says all apps for Windows 8 should be built for "touch first, with a keyboard and mouse that work just as well as first class citizens."
Note the order of that statement - although Microsoft isn't pretending people's mouse and keyboard habit is going to be changed quickly, it expects developers to develop for touchscreens as their top priority.
Intel's fight to survive in the "post PC" era
Microsoft's announcement that Windows 8 will also run on low-power ARM processors was a shot over Intel's bow and an embarrassing acknowledgement that the chip-maker had failed in achieving its vision for the Atom platform.
Intel's vision for Atom has always been that the chips would come down to power consumption levels that would allow them to be used in smartphones and iPad-equivalent devices.
Instead, it has found itself churning out chips for millions of low-cost netbooks which ended up frustrating users with their sluggish speed running Windows and cost the whole computer industry money as sales of more profitable full-power notebooks dropped.
The chip giant - with many of the industry's best engineers and massive financial resources - simply hasn't been able to get the x86 architecture, along with the required controller chips, down to the same computing-power-per-watt levels as the low-power reduced instruction set (RISC) system-on-a-chip designs made by ARM licensees.
Intel's phenomenal market power has largely been tied to Microsoft's success in keeping the world hooked on the combination of Windows and Office.
Now, with Microsoft announcing Windows will run on ARM architecture, the stakes are even higher for Intel in the mobility space.
iPad and Android devices already run on ARM architecture, and once Windows and Office are on ARM (Microsoft CEO Steve Ballmer has already hinted that Office will be rebuilt to work in the Metro interface, thus being available for ARM), the few holdout manufacturers trying to make x86 Windows tablet devices in form factors competitive with the iPad will have even less reason to stick with Intel.
Intel says it has this problem under control. It has merged its Atom and Core architecture teams, and will have 32nm Atom "Medfield" CPUs suitable for use in devices as thin as 9mm by next year.
How Windows 8 gets more from less
One of the defining characteristics of the "Wintel" marriage over the years has been an arms-race of ever-fatter software needing ever-faster chips.
This has suited Intel well, because one thing it has proven to be good at is squeezing more and more speed out of the x86 architecture, while (mostly) keeping its chips cool enough to be used in mainstream notebooks and desktops.
Apple boss Steve Jobs had controversially different ideas about how to keep power consumption manageable for very slim and light devices.
For the iPad, Jobs threw out the early '90s idea of pre-emptive multitasking, which lets any number of programs run at once, with the CPU constantly providing slices of time to each app.
The key problem with pre-emptive multitasking is that it's up to apps how much CPU time they chew up - the operating system exists to fulfill those requests, not keep them to a minimum.
Instead, Jobs' approach was initially to deny third-party apps any multitasking at all, ensuring iOS could tightly control CPU utilization, and hence, battery-life.
Under sustained criticism that this approach was too limiting, he softened it to allow limited multitasking, but only for three specific purposes: location tracking, music playback and VoIP connectivity.
All other forms of background activity have to run on cloud servers, in data centres where power consumption isn't constrained.
When one of these services wants to alert the user to something, such as new instant message, it sends a request to Apple's servers, which in turn send an alert to a user's iPad or iPhone. When a user sees the alert and chooses to act on it, only then is the app thawed from its frozen background state.
It's a clever idea, and surprisingly, despite Apple's relative lack of nous in internet services, it actually works and wasn't Google's idea. In fact, Android still uses pre-emptive multitasking, and suffers the performance problems and battery life issues intrinsically associated with it.
Microsoft is taking cues from this approach in Windows 8, too. Apps that aren't visible on screen will automatically go into a suspended state.
"Apps also auto-suspend themselves; they remain loaded in memory but take no CPU cycles at all. They're in a freeze-dried state, because I can't see them," said Sinofsky, as he demonstrated Windows 8 to BUILD conference attendees in September. "That's one of the ways we get extended battery life with Windows 8."
It's not yet clear how Windows 8 will deal with apps that are very much designed to run in the background without a visible window, like BitTorrent or Skype.
Windows boss Sinofsky is on the front foot about Windows performance, given the perception that Microsoft has bolted on an entirely new user interface layer on top of another one.
"I know you are thinking: 'You guys are going to add a bunch of code. And then Windows is going to get bigger. And it's going to get slower. And you're going to layer all this on top, and you're going to lose sight of fundamentals. You know what, we didn't. I promise you. We did not lose sight of fundamentals.'"
He demonstrated Windows 7 and Windows 8 running on the same model of Lenovo netbook - a three-year-old model with 1GB RAM and an early Atom processor. Windows 7 SP1 used 404MB of memory with 32 processes running, but Windows 8 only used 281MB of memory with 29 processes - "and that includes the anti-virus running that's built into Windows 8 Defender," Sinofsky said proudly.
A triumphant return to the PC era?
One thing is obvious about Microsoft's approach with Windows 8: it considers everything that you don't hold up to your ear (and make phone calls on) a PC.
Windows 8 on a desktop machine with three graphics cards running in SLI mode? PC. Ultra-thin notebook with a touchscreen? PC. Tablet with an ARM processor? PC.
With Windows 8, Microsoft doesn't care what hardware you run it on, it just wants to provide a one-size-fits-all operating system that can genuinely adapt to different screen sizes and interface styles.
This is undoubtedly a gamble for Microsoft, which has always preferred to rock the boat as little as possible lest it derail its gravy train of corporate clients - but it's clear that this time round, it has put real thought into how it can provide one OS to work on multiple different types of devices.
It is not providing a half-arsed "Windows 8 Tablet Edition" like it has with previous editions of Windows. It is just providing Windows 8, designed to work well on tablets all the way through to servers.
For example, Windows 8's much more tightly-controlled multitasking should allow devices to get much better battery life than they did with any previous version of Windows. It will also allow chips that lack full processing oomph - such as Intel Atom CPUs - to provide snappier performance for foreground apps.
Microsoft is also comprehensively addressing the problem of Windows' slow bootup and shutdown. The long-promised shift to universal extensible firmware interface (UEFI) as a replacement for the 25-year-old BIOS is finally happening.
Windows 8 achieves cold boot speeds of as little as three or four seconds by storing the kernel (but not apps) in a disk-hibernated state even when a computer is fully "shut down". A cold boot still reinitialises device drivers, giving the appearance of a freshly booted machine, as faulty drivers are the cause of most Windows suspend/resume problems.
At the BUILD conference, Microsoft demonstrated a PC booting from a cold start in less than four seconds, almost faster than the monitor could switch on.
Microsoft also now clearly understands the importance of the iPad's instant suspend/resume in terms of how consumers perceive the device. It is making one-second resume part of the Windows 8 hardware spec.
Most importantly, though, Microsoft is promising the full PC experience on anything from tablets up. Without naming the iPad specifically, Steven Sinofsky talks a lot about how restricted the tablet experience on competitors' tablets is when it comes to passing information between apps. And he's right.
"We have this bold notion that apps should work together as a web of apps on your machine. When you get more apps, the system just gets richer. So when I write an app, other apps automatically know how to pull information from or push it to my app."
"People want richer connectivity and sharing between applications. The idea that applications are silos, and don't talk to each other, or talk to each other through very narrow interfaces, that's not a rich enough interaction model for customers. They don't want apps to stand alone - they want a web of applications."
If Microsoft can pull it off, it may well see the Return of the Jedi - geeks wielding tablets with full Windows power but iPad-equalling battery life and form factor.
When you can buy a tablet with an OS that works more seamlessly with your Windows desktop environment and its apps than the iPad does with a Mac; when IT departments who've been holding back from integrating iPads into corporate systems get a Windows tablet they understand, and when as a consumer you can operate in a Windows-based PC, Ultrabook, tablet and smartphone ecosystem, it's hard to see how Apple - and not Wintel - will dominate the so-called post PC era.