The co processor approach, while attractive on surface, cannot explain the need for an arch license imo.
What I've been told is that you can't add a coprocessor to modern ARM designs anymore, it isn't something that's brought off of the RTL. So you do need an arch license for this.
ToTTenTranz said:
Well, I'd rather have AMD and Intel shrinking and optimizing their x86 APUs into small devices, guaranteeing compatibility between desktop and mobile OS/drivers/APIs, than having ARMs crawling their way up into desktops/notebooks.
Even if (apparently) people do consider ARM's architectures as "superior" from a power/performance perspective.
Intel is clearly trying to get there, AMD not really yet. You say you want x86 to be on mobiles for OS/kernel level compatibility, but then suggest that Windows for ARM means that MS wants to move ARM onto notebooks and desktops. Isn't it more likely that MS wants to move Windows down onto platforms currently dominated by ARM, like tablets?
It's not just the ARM is better for perf/Watt at the market segments it's currently targeting vs the current competition, but it's that ARM is by far the established regime. x86 obviously still has the desktop market, and the desktop market has proven that it can move down quite a bit - to laptops, then to netbooks - but I think that for most people that's pretty much the limit of its appeal. There are UMPCs, but those never exactly caught on. MS (and probably Intel) must have thought that tablets would be a continuation of PCs moving down, but Apple has proven this wrong, with a tablet that's very much a mobile moved up a bit. And Apple had full control of this decision, since they could have made an OS X/x86 based tablet instead - they must have had some reasoning in their decision, and I think it paid off well, as the rest of the industry is largely following.
The way I see it, most of the mobile market just has too little pragmatic incentive to move to x86. Most are now using Linux kernels or OSes developed specifically with ARM support (iOS, Symbian, Windows Phone), none of which benefit from x86 (quite the contrary, many probably aren't ported to x86 right now). The only benefactor would be MS with Windows proper, but since that's not an established market it makes much more sense for them to want to accommodate ARM than for mobile hardware vendors to want to accommodate them with x86. Most users just don't care about running traditionally x86 locked software (which is actually mostly just PC games) on these platforms. The mobile software ecosystem has already supplanted this.
But it's a little moot since most drivers and APIs and kernel code is probably not very locked into instruction set.