Apple Silicon Macs versus ARM PCs
In a comment on my entry on how I don't expect to have an ARM-based PC any time soon, Jonathan said:
My big takeaway from the latest release of Apple laptops is that these new laptops aren't necessarily ARM laptops. [...]
When a person gets an Apple Silicon Mac, they are not getting an ARM computer. They are getting an Apple computer.
As it happens, I mostly agree with this view of the new Apple
machines (and it got some good responses on tildes.net).
These Apple Silicon Macs are ARM PCs in that they are general purpose
computers (as much as any other
OS X macOS machine)
and that they use the ARM instruction set. But they are not 'ARM
PCs' in two other ways. First, they're not machines that will run
any OS you want or even very many OSes. The odds are pretty good
that they're not going to be running anything other than OS
X macOS any time soon (see Matthew Garrett).
Part of that is because these machines use a custom set of hardware around their ARM CPU and Apple has no particular reason to document that hardware so that anyone else can talk to it. In the x86 PC world, hardware and BIOS documentation exists (to the extent that it does) and standards exist (to the extent that they do) because there are a bunch of independent parties all involved in putting machines together, so they need to talk to each other and work with each other. There is nothing like that in Apple Silicon Macs; Apple is fully integrated from close to the ground up. The only reason Apple has for using standards is if they make Apple's life easier.
(Thus, I suspect that there is PCIe somewhere in those Macs.)
Second, they don't use standard hardware components and interfaces. This isn't just an issue of being able to change pieces out when they break or when they don't fit your needs (or when you want to improve the machine without replacing it entirely). It also means that work to support Apple Silicon Macs doesn't help any other hypothetical ARM PC, and vice versa. To really have 'ARM PCs' in the way that there are 'x86 PCs', you need standards, and to get those standards you probably need component based systems. If everyone is making bespoke SoC machines, you have to pray that they find higher level standards compelling, and those standards are useful enough.
(Even laptop x86 PCs are strongly component based, although often those components are soldered in place. This is one reason why Linux and other free OSes often mostly or entirely just works on new laptop models.)
PS: My feeling is that there is no single 'desktop market' where we can say that it does or doesn't want machines with components that it can swap or mix and match. There is certainly a market segment that demands that, and a larger one that wants at least the lesser version of adding RAM, replacing the GPU, and swapping and adding disks. But there is also a corporate desktop market where they buy little boxes in a specific configuration and never open them, and I suspect it has a bigger dollar volume.