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Apple: No Macintosh Forks. But the iPad...

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Re: Apple: No Macintosh Forks. But the iPad...

#111

Post by yoz-y »

_ph_ wrote: post #74
ken wrote: post #60

Every analysis I've read, including this one, assumes that Apple would start at the bottom rather than the top, as they have with every other CPU transition in the history of the company. Is there something especially difficult about making a high-core-count CPU? The A-series is already crushing single-threaded performance and they're competitive with Intel desktop CPUs for some applications. Once you have a high-per…

It isn't especially difficult, but is is expensive. The big challenge with CPU design is to make up for the costs and for that you need numbers. In the 90ies, there were plenty of high-performance CPU designs, Alpha, Sparc, Mips. They were alle killed by two mechanisms, that Intel had a lead in fab technology and that Intel had much higher numbers, consequentely could gain back much higher investments as the competit…

But Apple does not need to be a good or efficient fab because TSMC and Global Foundries already exist. One of the cited reasons for ARM transition is specifically that Intel fab sucks and their CPUs have been lagging in performance per watt for years.

Re: Apple: No Macintosh Forks. But the iPad...

#112

Post by gridlockd »

mjg59 wrote: post #61
Moto7451 wrote: post #4

I don’t think the argument holds very well. Apple has made three processor architectural changes including one on the current OS. “Too complicated” doesn’t really align with the execution history Apple has. The fat binary support Apple has is a huge tool and the ability to add instructions and optimizations to their chips to help with x86 emulation is a big deal. I don’t know if Apple will ever actually do this, but…

Apple has made two transitions while retaining compatibility, in one case with emulation of the old architecture being around the speed of the previous (68k to PPC) and in the other with emulation being faster than the previous architecture (PPC to x86). There's no ARM that's fast enough to emulate an x86 in the same power envelope, so right now any transition would either require all performance sensitive apps to be…

> ...with emulation being faster than the previous architecture (PPC to x86).

This is not the history that I remember, at least with contemporary hardware. In my recollection, PPC emulation was generally slower, but it didn't necessarily really matter.

> There's no ARM that's fast enough to emulate an x86 in the same power envelope, so right now any transition would either require all performance sensitive apps to be ported or would result in machines that were slower for many tasks.

I don't think that's true, at least at the lower end.

Whether it is running x86 emulation or native, the Snapdragon 835 comes pretty close to the Celeron N3450, at least in terms of single-core performance. Both chips have a comparable power envelope.

https://www.techspot.com/review/1599-windows-on-arm-performa...

Emulation adds overhead of course, but it's worth noting that most ISAs are effectively emulated through micro-operations:

https://en.wikipedia.org/wiki/Micro-operation

Re: Apple: No Macintosh Forks. But the iPad...

#113

Post by simonh »

Moto7451 wrote: post #4

I don’t think the argument holds very well. Apple has made three processor architectural changes including one on the current OS. “Too complicated” doesn’t really align with the execution history Apple has. The fat binary support Apple has is a huge tool and the ability to add instructions and optimizations to their chips to help with x86 emulation is a big deal. I don’t know if Apple will ever actually do this, but…

The key argument is that transitioning low to mid end Macs isnt enough. They would also need to transition the high end pro machines. That would require engineering super high performance, massively multi core ARM CPUs with huge IO throughput, that would only sell in the tens of thousands of units range.

There is just no way on earth they could ever be economically viable. The economies of scale are just dire. Intel can only do it because they sell many hundreds of thousands, or even millions of these high end CPUs, not just a few tens of thousands.

So the real point of contention is, does it make sense to only transition part of the Mac lineup to ARM if this is correct?

Re: Apple: No Macintosh Forks. But the iPad...

#114

Post by snazz »

yoz-y wrote: post #111
_ph_ wrote: post #74

Earlier quoted context omitted.

It isn't especially difficult, but is is expensive. The big challenge with CPU design is to make up for the costs and for that you need numbers. In the 90ies, there were plenty of high-performance CPU designs, Alpha, Sparc, Mips. They were alle killed by two mechanisms, that Intel had a lead in fab technology and that Intel had much higher numbers, consequentely could gain back much higher investments as the competit…

But Apple does not need to be a good or efficient fab because TSMC and Global Foundries already exist. One of the cited reasons for ARM transition is specifically that Intel fab sucks and their CPUs have been lagging in performance per watt for years.

Performance per watt isn’t too important on the Mac Pro and the low volumes mean that developing a purpose-built chip would be extremely cost-prohibitive.

Re: Apple: No Macintosh Forks. But the iPad...

#115

Post by imtringued »

gridlockd wrote: post #112
mjg59 wrote: post #61

Earlier quoted context omitted.

Apple has made two transitions while retaining compatibility, in one case with emulation of the old architecture being around the speed of the previous (68k to PPC) and in the other with emulation being faster than the previous architecture (PPC to x86). There's no ARM that's fast enough to emulate an x86 in the same power envelope, so right now any transition would either require all performance sensitive apps to be…

> ...with emulation being faster than the previous architecture (PPC to x86). This is not the history that I remember, at least with contemporary hardware. In my recollection, PPC emulation was generally slower, but it didn't necessarily really matter. > There's no ARM that's fast enough to emulate an x86 in the same power envelope, so right now any transition would either require all performance sensitive apps to be…

>Emulation adds overhead of course, but it's worth noting that most ISAs are effectively emulated through micro-operations

That's not even remotely the same thing because that micro-code is optimized to the ISA of the processor and it's obviously specific to the microarchitecture of the processor which is again optimized for a specific ISA. It's like translating a Wikipedia article from normal English to simple English. You didn't cross a complicated language barrier.

If I may add my own comment: It's not worth noting at all because your ARM CPU still only implements ARM optimizations and your x86 CPU only implements x86 optimizations.

If you had proposed adding hardware acceleration to make emulation of a specific architecture faster then maybe one could have squinted and said it's emulation instead of secretly implementing a x86 CPU in your ARM CPU.

Re: Apple: No Macintosh Forks. But the iPad...

#116

Post by coldtea »

Laforet wrote: post #34
runjake wrote: post #11

For some context: the author of this article, Jean-Louis Gassée, was a former director at Apple, founded Be, Inc. and was chairman at PalmSource for a while. His background may help or hurt his viewpoint, depending on how you see things. I will say that I disagree with his points. And I'll also point out that the Mac ARM transition is happening right before our eyes with the T2 chip , which replaces a bunch of system…

I can't help but feel T2 chip is just another cynical ploy to gradually kill off third party repairs by baking software functions into proprietary hardware that only the manufacturer have access to. It may be a sound security decision, but I have doubts whether it's worth it for the end user. It also goes against a wider industrial trend of moving from ARM to RISCV and other architectures. On the other hand, do all t…

>I can't help but feel T2 chip is just another cynical ploy to gradually kill off third party repairs by baking software functions into proprietary hardware that only the manufacturer have access to.

Not very cynical: Apple is against "third party repairs" period, and wants to sell you the whole thing as a black box.

They also believe that's their whole value proposition: that software and hardware comes as much as possible as a black box, and works well together (not perfect, but better than if it wasn't a black box for the aspects that they focus on - simplicity, integration, security, sandboxing, etc).

That's their stance, and they got to where they are from near bankruptcy, sales wise, in pursuit of that.

>It also goes against a wider industrial trend of moving from ARM to RISCV and other architectures.

What "wider industrial trend"?

Re: Apple: No Macintosh Forks. But the iPad...

#117

Post by coldtea »

jart wrote: post #19
runjake wrote: post #11

For some context: the author of this article, Jean-Louis Gassée, was a former director at Apple, founded Be, Inc. and was chairman at PalmSource for a while. His background may help or hurt his viewpoint, depending on how you see things. I will say that I disagree with his points. And I'll also point out that the Mac ARM transition is happening right before our eyes with the T2 chip , which replaces a bunch of system…

Is the struggle for microprocessor supremacy still even relevant? I'd ask, "who's going to build the best quantum processor?" rather than, "who's going to dethrone x86?"

>who's going to build the best quantum processor?

Nobody. Besides quantum processors are not general purpose, and as thus, they're of no real consequence for the kind of computing 99% of people do...

Re: Apple: No Macintosh Forks. But the iPad...

#118

Post by coldtea »

ajconway wrote: post #88
mjg59 wrote: post #61

Earlier quoted context omitted.

Apple has made two transitions while retaining compatibility, in one case with emulation of the old architecture being around the speed of the previous (68k to PPC) and in the other with emulation being faster than the previous architecture (PPC to x86). There's no ARM that's fast enough to emulate an x86 in the same power envelope, so right now any transition would either require all performance sensitive apps to be…

Apple sells iPad Pros which they call “computers”. Those are powerful devices, but there is not much productivity software available, and UI is very different from traditional desktop interfaces. Apple could offer an Air-class machine powered by ARM with a familiar macOS, and most developers would be able to support it in a matter of weeks, if not days.

>but there is not much productivity software available

Huh? There is more productivity software available for iPad's than for a PC in 1995.

Re: Apple: No Macintosh Forks. But the iPad...

#119

Post by imtringued »

SkyMarshal wrote: post #36
reitzensteinm wrote: post #24

I don't buy the permanent fork argument for one reason. AMD had the cancelled ARM version of Zen. There aren't any public plans to bring it back as far as I'm aware. But if Apple transitions past x86, it's going to provide critical mass for desktop ARM and the Zen chip will be back. AMD would be sitting on the highest performance single socket ARM chip, and Apple would just use that.

I can't see Apple using any ARM chip other than their own. If they commit to converting OS X to ARM then they'll either produce it in-house or, less likely, buy AMD (or maybe just buy AMD's Zen tech only). One of the main reasons for Apple to move to ARM is to control more of their technology stack. It's the direction they've been moving in for a while now and this would be part of that strategy.

Macs don't have enough sale volume to have multiple SoCs. Heck even iPhones and iPads share the same SoC. They can't justify having a new SoC for each of their Macbook, Macbook Pro, iMac and the Mac Pro with dozens of cores. If they transition to ARM then half of their Mac lineup will still stay on x86.

Re: Apple: No Macintosh Forks. But the iPad...

#120

Post by twoodfin »

yoz-y wrote: post #90
vlozko wrote: post #62

Earlier quoted context omitted.

There’s definitely some common threads with this and Apple’s push to have apps use bitcode. It would make this duality a lot easier from an app distribution perspective without the need to have an emulation layer. My only guess as to why Apple hasn’t required bitcode by now is the sheer number of 3rd party libraries out there that aren’t built with bitcode enabled.

Chris Lattner has stated several times that bitcode does not help with porting to other platforms though

He’s said since that while that was true when he left Apple, they have clearly made strides in the direction of making bitcode platform-neutral. Notably the shift from 32-bit to 64-bit ARM on the Watch was totally transparent to developers; they didn’t even need to resubmit their apps. And that’s not a small architectural change.
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