Posted by: Ed Tittel
hardware abstraction makes Windows on ARM easier than it might look, WOA exploits HAL for Windows 8
You’ve gotta love Paul Thurrott and his Supersite for Windows. In a recent blog (Valentine’s Day 2012, same title as the quote in my blog lead for today) he articulates clearly some very interesting thoughts about Windows on ARM, aka WOA, not just in terms of what it could mean, but also in terms of where it comes from. And he does so with great humor and even a bit of old-fashioned story-telling.
To really get the point of WOA (and his blog) it helps to remember that part of Windows that goes all the way back to the original NT release in 1992 (called Windows NT 3.1 to synch up with the “other Windows” that prevailed at the time). It’s called the HAL, which stands for Hardware Abstraction Layer, and is best understood as a sort of CPU über-driver (or as a CPU-family-specific “operating system driver,” if you will). In fact, HAL lives on quite happily in the latest Windows versions, including Windows 7 and Windows Server 2008 R2 (and even in Windows 8).
In his post, Thurrott reminds us that when the HAL was introduced in its earliest days, Intel and AMD did not completely rule the PC landscape with their x86 (Intel) and x64 (AMD) architectures. So, Windows NT was built to run on other CPUs as well, including PowerPC, the DEC Alpha, and MIPS processors (anybody remember those?) through custom-building HALs for each one. Later on, the same technique was also put to work for Intel’s Itanium processor as well.
Well guess what? The same technology — and the same hard work to build a new HAL — makes it doable to bring the ARM processor into the Windows fold. But Microsoft has gotten smart about the needs of mobile processors for small, power-efficient code and has further decided NOT to bring x86/x64 support into its Windows on ARM (WOA) implementation. Yeah, sure, this will cause heartburn for those who think they want to run standard Windows apps on ARM-based devices, but this is one can of worms that Microsoft has decided not to open in WOA container. Metro-style apps only for WOA, so as to be sure to sip power, work well with touch GUIs, and leave lots of legacy problems and heartaches behind (especially where security is concerned).
Thurrott makes the point that “what’s old is new again” (a proverb, not a quote from his story) thanks to this built-in facility that dates back to the first NT release. I agree wholeheartedly, and wonder what kinds of interesting capabilities lie ahead thanks to this WOA design.