Memory access on the Apple M1 processor • Hacker News Board

Re: Memory access on the Apple M1 processor

#91

Post by coldtea » Wed, Jan 06, 2021, 8:46 PM UTC

pdpi wrote: post #20

jeffbee wrote: post #2

Great practical information. Nice to see people who know what they are talking about putting data out there. I hope eventually these persistent HN memes about M1 memory will die: that it's "on-die" (it's not), that it's the only CPU using LPDDR4X-4267 (it's not), or that it's faster because the memory is 2mm closer to the CPU (not that either). It's faster because it has more microarchitectural resources. It can load…

This seems to be a recurring theme with the M1, and one that, in a sense, actually baffles me even more than the alternative. There is no "magic" at play here, it's just lots and lots of raw muscle. They just seem to have a freakishly successful strategy for choosing what aspects of the processor to throw that muscle at. Why is that strategy simultaneously remarkably efficient and remarkably high-performance? What en…

>Why is that strategy simultaneously remarkably efficient and remarkably high-performance? What enabled/led them to make those choices where others haven't?

The things people give them complains about:

(a) keeping a walled garden,

(b) moving fast and taking the platform to new directions all at once

(c) controlling the whole stack

Which means they're not beholden to compatibility with third party frameworks and big players, or with their own past, and thus can rely on their APIs, third party devs etc, to cater to their changes to the architecture.

And they're not chained to the whims of the CPU vendor (as the OS vendor) or the OS vendor (as the CPU vendor) either, as they serve the role of both.

And of course they benchmarked and profiled the hell out of actual systems.

Re: Memory access on the Apple M1 processor

#92

Post by fartcannon » Wed, Jan 06, 2021, 8:55 PM UTC

coldtea wrote: post #91

pdpi wrote: post #20

Earlier quoted context omitted.

This seems to be a recurring theme with the M1, and one that, in a sense, actually baffles me even more than the alternative. There is no "magic" at play here, it's just lots and lots of raw muscle. They just seem to have a freakishly successful strategy for choosing what aspects of the processor to throw that muscle at. Why is that strategy simultaneously remarkably efficient and remarkably high-performance? What en…

> Why is that strategy simultaneously remarkably efficient and remarkably high-performance? What enabled/led them to make those choices where others haven't? The things people give them complains about: (a) keeping a walled garden, (b) moving fast and taking the platform to new directions all at once (c) controlling the whole stack Which means they're not beholden to compatibility with third party frameworks and big…

They could still do all this shit without the walled garden. To me, it suggests they aren't willing to compete. They're anti-competitive.

Re: Memory access on the Apple M1 processor

#93

Post by megablast » Wed, Jan 06, 2021, 8:59 PM UTC

jeffbee wrote: post #2

Great practical information. Nice to see people who know what they are talking about putting data out there. I hope eventually these persistent HN memes about M1 memory will die: that it's "on-die" (it's not), that it's the only CPU using LPDDR4X-4267 (it's not), or that it's faster because the memory is 2mm closer to the CPU (not that either). It's faster because it has more microarchitectural resources. It can load…

You’ll get people guessing, since Apple itself puts out so little information.

Re: Memory access on the Apple M1 processor

#94

Post by adam_arthur » Wed, Jan 06, 2021, 9:06 PM UTC

pdpi wrote: post #20

jeffbee wrote: post #2

Great practical information. Nice to see people who know what they are talking about putting data out there. I hope eventually these persistent HN memes about M1 memory will die: that it's "on-die" (it's not), that it's the only CPU using LPDDR4X-4267 (it's not), or that it's faster because the memory is 2mm closer to the CPU (not that either). It's faster because it has more microarchitectural resources. It can load…

This seems to be a recurring theme with the M1, and one that, in a sense, actually baffles me even more than the alternative. There is no "magic" at play here, it's just lots and lots of raw muscle. They just seem to have a freakishly successful strategy for choosing what aspects of the processor to throw that muscle at. Why is that strategy simultaneously remarkably efficient and remarkably high-performance? What en…

Certainly Apple's processors are far ahead, but they're a full process generation (5nm) ahead of their competitors. They paid their way to that exclusive right through TSMC.

I'm sure they'll still come out ahead in benchmarks, but the numbers will be much closer once AMD moves to 5nm. You absolutely cannot fairly compare chips from different fab generations.

I don't see many comments hammering this point home enough... it's not like the performance gap is through engineering efforts that are leagues ahead. Certainly some can be attributed to that, and Apple has the resources to poach any talent necessary.

Re: Memory access on the Apple M1 processor

#95

Post by wmf » Wed, Jan 06, 2021, 9:08 PM UTC

adam_arthur wrote: post #94

pdpi wrote: post #20

Earlier quoted context omitted.

This seems to be a recurring theme with the M1, and one that, in a sense, actually baffles me even more than the alternative. There is no "magic" at play here, it's just lots and lots of raw muscle. They just seem to have a freakishly successful strategy for choosing what aspects of the processor to throw that muscle at. Why is that strategy simultaneously remarkably efficient and remarkably high-performance? What en…

Certainly Apple's processors are far ahead, but they're a full process generation (5nm) ahead of their competitors. They paid their way to that exclusive right through TSMC. I'm sure they'll still come out ahead in benchmarks, but the numbers will be much closer once AMD moves to 5nm. You absolutely cannot fairly compare chips from different fab generations. I don't see many comments hammering this point home enough.…

From a customer's perspective it's not my problem. Everyone had the opportunity to bid on that fab capacity and they decided not to.

Re: Memory access on the Apple M1 processor

#96

Post by PragmaticPulp » Wed, Jan 06, 2021, 9:15 PM UTC

jeffbee wrote: post #2

Great practical information. Nice to see people who know what they are talking about putting data out there. I hope eventually these persistent HN memes about M1 memory will die: that it's "on-die" (it's not), that it's the only CPU using LPDDR4X-4267 (it's not), or that it's faster because the memory is 2mm closer to the CPU (not that either). It's faster because it has more microarchitectural resources. It can load…

I don't understand this competition to attribute the M1's speed to one specific change, while downplaying all of the others.

M1 is fast because they optimized everything across the board. The speed is the cumulative result of many optimizations, from the on-die memory to the memory clock speed to the architecture.

Re: Memory access on the Apple M1 processor

#97

Post by adam_arthur » Wed, Jan 06, 2021, 9:20 PM UTC

wmf wrote: post #95

adam_arthur wrote: post #94

Earlier quoted context omitted.

Certainly Apple's processors are far ahead, but they're a full process generation (5nm) ahead of their competitors. They paid their way to that exclusive right through TSMC. I'm sure they'll still come out ahead in benchmarks, but the numbers will be much closer once AMD moves to 5nm. You absolutely cannot fairly compare chips from different fab generations. I don't see many comments hammering this point home enough.…

From a customer's perspective it's not my problem. Everyone had the opportunity to bid on that fab capacity and they decided not to.

Yeah, totally agreed. But if you read these comments, they seem to be in total amazement about the performance gap and not acknowledging how much of an advantage being a fab generation ahead is.

Customers don't care, but discussion of the merits of the chip should be more nuanced about this.

It also implies that the gap won't exist for very long, as AMD will move onto 5nm soon

Re: Memory access on the Apple M1 processor

#98

Post by FabHK » Wed, Jan 06, 2021, 9:22 PM UTC

kllrnohj wrote: post #83

saagarjha wrote: post #77

Earlier quoted context omitted.

It is in memory performance, which is what I assumed was being measured here.

How are you defining memory performance and where are your supporting comparisons? This article only discusses the M1's behavior, and makes no comparisons to any other CPU.

FWIW, I ran it on a MacBook Pro (13-inch, 2019, Four Thunderbolt 3 ports), 2.4 GHz Quad-Core Intel Core i5, 8 GB 2133 MHz LPDDR3:

  two  : 49.6 ns  (x 5.5)
  two+ : 64.8 ns  (x 5.2)
  three: 72.8 ns  (x 5.6)

EDIT to add: above was just `cc`. Below is with `cc -O3 -Wall`, as in Lemire's article:

  two  : 62.8 ns  (x 7.1)
  two+ : 69.2 ns  (x 5.5)
  three: 95.3 ns  (x 7.3)

Re: Memory access on the Apple M1 processor

#99

Post by marrvelous » Wed, Jan 06, 2021, 9:28 PM UTC

fartcannon wrote: post #92

coldtea wrote: post #91

Earlier quoted context omitted.

> Why is that strategy simultaneously remarkably efficient and remarkably high-performance? What enabled/led them to make those choices where others haven't? The things people give them complains about: (a) keeping a walled garden, (b) moving fast and taking the platform to new directions all at once (c) controlling the whole stack Which means they're not beholden to compatibility with third party frameworks and big…

They could still do all this shit without the walled garden. To me, it suggests they aren't willing to compete. They're anti-competitive.

With the walled garden, Apple can set enforceable timelines for the software ecosystem to adopt to architectural changes.

Remember the transition to arm64? Apple forced everything on the App Store to ship universal binaries.

Without the App Store walled garden, software isn’t required to keep up to date with architectural changes. Instead, keeping current is only a requirement to being featured on the App Store (which would just be a single way to install software, not the only method).

Re: Memory access on the Apple M1 processor

#100

Post by danaris » Wed, Jan 06, 2021, 9:29 PM UTC

jeffbee wrote: post #69

gameswithgo wrote: post #24

Earlier quoted context omitted.

What other laptop ships with LPDDR4X clocked at 4267? I agree though that being closer to the cpu isn't having any appreciable effect on latency, but being soldered close to the cpu probably does make it easier for them to hit that high clock rate.

As WMF mentions, Tiger Lake laptops like my Razer Book have the same memory. It is not appreciably closer to the CPU in the Apple design. In Intel's Tiger Lake reference designs the memory is also in two chips that are mounted right next to the CPU.

And (genuine question) how do the Tiger Lake laptops compare with the M1 MacBooks thus far?