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The porting was obvious, the switching was not.

Agreed, but that's not what I'm annoyed by here.

The porting was obvious, the switching was not.

It was obvious to me, knowing that MacOS is based on NeXTStep and how that ran on a bunch of different architectures—68000, Intel, Sparc, etc.

I even wrote 3 years ago here on HN (before Apple announced their transition to ARM) that I wouldn't be surprised if there were ARM-based Macs in the lab [1].

And also knowing that Apple always wants to be in control of as much of the technology they rely on as possible. After Motorola/IBM dropped the ball with PowerPC and Intel couldn't deliver the performance per watt they needed, they weren't going to fooled a third time.

[1]: https://news.ycombinator.com/item?id=21235236

No, the porting is obvious - I guarantee Apple has test rigs running Darwin on AMD processors and RISC-V, for example - but switching, as in, actually doing something with that portability, is less obvious.

I guess what I'm saying is that it's not at all interesting or surprising that someone in 2014 prognosticated that MacOS X had been ported to ARM.

I literally wrote the same thing about NeXTSTEP here on HN 3 years ago: https://news.ycombinator.com/item?id=21235236

> When iOS was developed on the iPhone, it was obvious that it was little more than a modified version of MacOS X

They said exactly this at the time. The OS on the original iPhone was explicitly “OS X”, it only gained its own name several iterations later.

What made NeXT (and then OS X) so portable? NeXT never sold a whole lot, but I would like to see a breakdown of sales by CPU. And if certain platforms were missing things, etc.

I've heard many answers over the years:

Mach is a microkernel, they are easier to port

NeXT never made their own hardware so they designed it that way from the start

It contained 'very little assembly'

> NeXT never made their own hardware so they designed it that way from the start

When I think NeXT, I think the NeXTcube (1990-1993) [0], which apparently also had a predecessor in the NeXT Computer (1988-1991) [1]. NeXT made their own hardware for a solid chunk (nearly half) of their lifespan, and NeXTSTEP was originally released with the NeXT Computer [2]. It didn't even support CPU architectures other than the Motorola 68k series until 1993, around the demise of the NeXTcube! I think its ultimate portability probably has more to do with being a UNIX at its core (so a battle-tested design written in somewhat portable C) plus a user environment written in a higher-level, easier to port language (Objective-C).

[0]: https://en.wikipedia.org/wiki/NeXTcube [1]: https://en.wikipedia.org/wiki/NeXT_Computer [2]: https://en.wikipedia.org/wiki/NeXTSTEP

I meant their own CPU

The "NeXT Cube" was essentially the same thing as the "NeXT Computer" with an updated CPU. Basically, they renamed it after they released the "NeXTstation"[0] to avoid confusion. Otherwise, they'd have had two NeXT "Computers." Heh.

Though fine in 1988, NeXT's own hardware was rather under-powered for the early 90's. Their main competitor, Sun, was transitioning to their own RISC architecture (SPARC) after originally being on 68K. DEC was coming out with the Alpha. HP had moved to PA RISC. Though I digress, it's too bad NeXT never ran on the Alpha! That would've been a killer 90's setup.

[0]: https://en.wikipedia.org/wiki/NeXTstation

Super good question. I owned and used NeXT slabs, 1992 - 1999.

The Mach-as-microkernel thing couldn't have helped portability. The Mach task, port, thread and pager abstractions seem like they'd be difficult to port, but I could be wrong.

I read at the time that NeXTStep the GUI ran faster on Solaris than on Mach, because pipes and sockets were faster than Mach ports. So I'll believe the very little assembly.

I suspect that Mach-O file format had something to do with the portability, you can put arbitrary sections in it. Some NeXT games kept image and sound "files" in a single huge Mach-O executable.

The impression I always got from those abstractions were that they were precisely there to support portability. Pagers, for example, are quite flexible about what can back them and what the geometry of that backing can be.

Yes, but it was explicitly a different kind of portability: running MSDOS or VMS executables unchanged, for example.

The task/port/thread/pagers are primitives that let Mach run some other OS executables, not made it easy to port Mach to other hardware. There were papers about getting MSDOS and VMS executables to run in Mach tasks. Some startup was making a system to run (pre-OSX) Mac executables.

Early in that timeline Solaris was heavily into being a "pure" System V r4. The pipes and sockets implementations were based on System V Streams -- the in joke was that streams were much more like sewers and they weren't pleasant. Numbers wise, they were perhaps 2 orders of magnitude slower than on SunOS (BSD based). At one state university, where a very "beefy" SPARCcenter 2000 was purchased to support 500 simultaneous users, Solaris on this system could barely support 40 users (streams performance was the reason - telnet sessions pushed several streams modules). Sun ended up having to provide 10 SPARCstation 10 systems running SunOS which could easily support 70 simultaneous users each in order to fulfill the contractual obligations. The SPARCcenter 2000 was turned into an NFS file server.

After the early days, Solaris did improve, but I think that was because ideas / pieces of BSD (from SunOS) were put back into the OS.

I don't think Solaris pipes / sockets performed better than Mach.

Early Solaris was definitely not very good. I briefly ran Solaris 2.4 on a SparcStation 5, and reinstalled SunOS 4.1.x because Solaris 2.4 was so bad. 2.5 was decent though!

Mach more than helped:

"Mach 3 (Figure B.1) moves the BSD code outside of the kernel, leaving a much smaller microkernel. This system implements only basic Mach features in the kernel; all UNIX-specific code has been evicted to run in user-mode servers. Excluding UNIX-specific code from the kernel allows replacement of BSD with another operating system or the simultaneous execution of multiple operating-system interfaces on top of the microkernel. In addition to BSD, user-mode implementations have been developed for DOS, the Macintosh operating system, and OSF/1. This approach has similarities to the virtual-machine concept, but the virtual machine is defined by software (the Mach kernel interface), rather than by hardware."

https://web.eecs.utk.edu/~qcao1/cs560/papers/mach.pdf

NeXT ran a Mach 2.0 variant. I forget which Mach features were absent, but NeXT unmistakeably ran 2.0

The BSD stuff was kind of bolted on. Very uneasy marriage there.

At one point DEC had a 2 Mach task system that could run VMS processes, but I'm pretty sure that was Mach 3.0 based.

That is to say, Mach 2.0 wasn't as advanced in portability, and the "portability" targeted was different.

Portable compared to what?

« microkernels are easier to port » is not a thing.

NeXT did make their own hardware, it was 680x0-based and it was nicer to use than the x86 PC shitboxes it ran on when they stopped making hardware.

« very little assembly » is closest to the truth. NeXTstep and OpenStep were written almost entirely in C and Objective-C and compiled using the GNU toolchain. NeXT was always a hybrid of Unix userspace on top of a Mach microkernel. It’s just not that hard to port a Unixlike OS to another CPU architecture. It’s literally been done since the 1970’s.

However, it is much more difficult to port the OS and maintain binary compatibility with apps created for the previous CPU architecture, which has always been Apple’s special sauce since the original PowerPC Macs.

The hardware certainly looked nice (I have a "turbo" slab in my collection!), but the performance was "meh" at best. NeXTstep needed a lot of resources, and late 680x0 was no match for an early Pentium. It's no wonder NeXT ported to x86.

I don't think running on a bunch of CPU architectures is really unique to NeXT. Windows NT ran/runs on x86, Arm, Alpha, MIPS, Itanium, and PowerPC, all with a desktop as a full-blown product. Forms of desktop Linux will run on all of those and more.

Short answer: small teams of Really Smart People.

Business necessity. Something about your own hardware business failing makes you really eager to port to other hardware architectures. That and your processor manufacturer (Motorola) openly indicating that they're killing the ISA you built your platform on.

Obv writing in a portable language and on a portable microkernel helps.

You vastly underestimate the effort involved in a port of something like an OS.

This comment left me shaking my head and facepalming all at once.

MacOS always ran on x86 chips. SJ admitted as much. There was always a skunk works project to keep OS X compatible with x86z

The parent comment wasn’t expression frustration at that, He was expression frustration at people thinking running OS X on arm way back when was some kind of feat.

At the time, it was.

This is a middlebrow dismissal. From what I can see this article played out exactly as predicted, and the idea that NeXTSEP rans on multiple architectures in the 90s is just half-assed retconning. In 2014 the conventional wisdom was that Intel was best-in-class and would remain dominant.

Per the other thread, I'm not seeing the storyline that the author is arguing that Mac OS will run on ARM but still be first class on Intel architecture. We can assume that is not the case because Apple doesn't half-ass their transitions.

Please highlight what you think the prediction got wrong so we can talk about that specifically.

I'm not dismissing the prognostication that Macs would ultimately run on ARM (though to be honest that was obvious a long time ago). I'm dismissing the breathless way in which the author announced that somewhere, somehow, a Mac was already running ARM in the bowels of Apple in 2014. Of course it was. It was doing that a decade prior.