There's a couple different things at play this time. Windows RT only allowed Store apps and Microsoft's own ARM desktop apps. Windows 10 on ARM will run UWP Store apps and x86 apps (desktop & hybrid "Centennial" apps). At at Build, they announced Edge support for Progressive Web Apps and they'll be adding PWAs to the Store automatically if they meet all the right criteria for features & quality.

So not only will this platform support almost all the existing Windows software out there, it'll treat PWAs as first-class citizens.

I think you missed that news : https://www.engadget.com/2017/05/12/windows-10-will-seamless...

Have there been any public previews of this? I'm still trying to figure out how they can emulate x86 without significant performance problems due to the different memory concurrency models

https://www.betaarchive.com/forum/viewtopic.php?f=62&t=37172... ARM64 Windows leaked - and can run in Qemu.

I have heard the concern re memory concurrency models, can somebody explain the problem a bit more?

This is basically an emulator though; it will be quite slow.

They showed games (WoT I think) running using this emulation, so maybe not.

"World of Tanks Blitz" - a Phone game

We don't know yet. Overhead could be something like 5% or 25%. We'll see when the reviews come. For what it's worth, it seems to run x86 apps just fine in Microsoft's own demo (keep in mind it's still a mobile ARM processor, so performance will be similar to Atom/Celeron/Pentium, rather than Core i5, etc).

https://www.youtube.com/watch?v=A_GlGglbu1U

I don't trust product demos, movie trailers nor press releases, so I'll reserve my enthusiasm until someone on the "real world" has had the chance to get their hands on this.

What I know is this: ARM emulation via QEMU on my core i7 was pretty slow last I tried it. Not unusably slow, but still slow. And I have tons of ram and a fat CPU.

These laptops, especially if they are made on the cheap side, won't have tons of RAM and a fat CPU. Unless Microsoft pulled some magic tricks, I don't see this emulation being usable.

But I could be wrong.

"faster than QEMU" isn't a particularly high bar to clear, though. In particular if you're only emulating a single process rather than a full guest OS then you can reduce the overhead quite a bit. Plus if you design something from the start for the single-process emulation case, and only need to worry about one guest and one host architecture, and focus on emulation performance as a key goal, you can likely do better than QEMU without too much trouble.

https://www.betaarchive.com/forum/viewtopic.php?f=62&t=37172... ARM64 emulation in Qemu is very slow anyway...

Emulation is slower but most people will be using browser/office/vscode etc so its just for those extra few apps that might stop you buying the product if emulation didn't exist.

that might not matter

x86 emulation will make life easier initially. But if these devices become popular, so will UWP apps.