Discussion Apple Silicon SoC thread

Eug · Nov 10, 2020

M1
5 nm
Unified memory architecture - LP-DDR4
16 billion transistors

8-core CPU

4 high-performance cores
192 KB instruction cache
128 KB data cache
Shared 12 MB L2 cache

4 high-efficiency cores
128 KB instruction cache
64 KB data cache
Shared 4 MB L2 cache
(Apple claims the 4 high-effiency cores alone perform like a dual-core Intel MacBook Air)

8-core iGPU (but there is a 7-core variant, likely with one inactive core)
128 execution units
Up to 24576 concurrent threads
2.6 Teraflops
82 Gigatexels/s
41 gigapixels/s

16-core neural engine
Secure Enclave
USB 4

Products:
$999 ($899 edu) 13" MacBook Air (fanless) - 18 hour video playback battery life
$699 Mac mini (with fan)
$1299 ($1199 edu) 13" MacBook Pro (with fan) - 20 hour video playback battery life

Memory options 8 GB and 16 GB. No 32 GB option (unless you go Intel).

It should be noted that the M1 chip in these three Macs is the same (aside from GPU core number). Basically, Apple is taking the same approach which these chips as they do the iPhones and iPads. Just one SKU (excluding the X variants), which is the same across all iDevices (aside from maybe slight clock speed differences occasionally).

EDIT:

M1 Pro 8-core CPU (6+2), 14-core GPU
M1 Pro 10-core CPU (8+2), 14-core GPU
M1 Pro 10-core CPU (8+2), 16-core GPU
M1 Max 10-core CPU (8+2), 24-core GPU
M1 Max 10-core CPU (8+2), 32-core GPU

M1 Pro and M1 Max discussion here:

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M1 Ultra discussion here:

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M2 discussion here:

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Second Generation 5 nm
Unified memory architecture - LPDDR5, up to 24 GB and 100 GB/s
20 billion transistors

8-core CPU

4 high-performance cores
192 KB instruction cache
128 KB data cache
Shared 16 MB L2 cache

4 high-efficiency cores
128 KB instruction cache
64 KB data cache
Shared 4 MB L2 cache

10-core iGPU (but there is an 8-core variant)
3.6 Teraflops

16-core neural engine
Secure Enclave
USB 4

Hardware acceleration for 8K h.264, h.264, ProRes

M3 Family discussion here:

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M4 Family discussion here:

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poke01 · Monday at 12:22 PM

poke01 said:
View attachment 110456
M4 supports 8K 120Hz display out via TB4 using DSC.

Not even the 4090 supports 8K 120Hz using DSC. Apple cooked with their display controllers. Remember, this is the base M4.

Most with a M4 will likely never use a 8K 120Hz display but hey it’s future proof.

Eug · Monday at 12:34 PM

Base iMac is using a binned chip.

Binned by CPU efficiency cores and GPU. CPU performance cores the same.

mvprod123 · Monday at 1:02 PM

poke01 said:
View attachment 110456
M4 supports 8K 120Hz display out via TB4 using DSC.

New Pro Display XDR confirmed?

Mopetar · Monday at 1:16 PM

soresu said:
Annoying as hell that 3D NAND keeps improving, but storage options in actual products seem to remain stagnant.

If they gave you enough storage you wouldn't pay the $$$ to upgrade to the next tier. They could just make that the baseline option, but then they'd just bake the extra $$$ into the price anyway.

poke01 said:
Not even the 4090 supports 8K 120Hz using DSC. Apple cooked with their display controllers. Remember, this is the base M4.

Most with a M4 will likely never use a 8K 120Hz display but hey it’s future proof.

It's just a consequence of them designing a new controller for their high-end machines that will have one or more 8K displays connected and not wanting to have two separate pieces of hardware to deal with.

Here's the opposite case where the iMac is over provisioned and has hardware most users don't need and wouldn't pay to upgrade.

johnsonwax · Monday at 1:52 PM

Eug said:
Base iMac pricing has stayed the same at US$1299, but now it starts at 16 GB memory. (256 GB storage stays the same.) However, 8 GB upgrade pricing (for a total of 24 GB) is still $200.

Reminder that Apple designs to price points. The iMac is now 26 years of having ~$1299 base price (a 49% discount factoring for inflation). Apples pricing, particularly upgrades have no relationship to component costs, but to perceived value to the customer - just like in every other industry. I'm sure there are people walking into the car dealership who know the component costs of a trim upgrade, but no normal car buyer is aware of that and that bears no real relationship to how we buy things. Only the tech industry remains fixated on this from a long history of building PCs from components, but hardly anyone does that now. Even the gamer market has not only SKUs to pick from, but whole OEMs that cater to them.

I am surprised they made the first RAM upgrade 24GB instead of going straight to 32. I do get the sense that Apple is succumbing to investor pressure more than they have historically done.

johnsonwax · Monday at 1:59 PM

mvprod123 said:
New Pro Display XDR confirmed?

Maybe. That's an odd bit of support to add to the base M4 unless it was so cheap to implement there was no point excluding it. Even then, it would seem more likely for Apple to keep it in and never certify it or enable it via software because that's such an obvious upsell to Pro feature. Depending on how small the new Mini form factor is, they might be trying to grab a bit of the high end display-focused market (medical imaging stations, kiosks, etc.) The mini has always been part of the home theater scene.

digitaldreamer · Monday at 2:03 PM

Eug said:
Base iMac is using a binned chip.

View attachment 110457

Binned by CPU efficiency cores and GPU. CPU performance cores the same.

And, that iMac only has two Thunderbolt / USB 4 ports and no Ethernet.

igor_kavinski · Monday at 2:06 PM

johnsonwax said:
The iMac is now 26 years of having ~$1299 base price (a 49% discount factoring for inflation).

Apple is always welcome to increase the base price by 49% and see how that goes for them.

Eug · Monday at 2:11 PM

digitaldreamer said:
And, that iMac only has two Thunderbolt / USB 4 ports and no Ethernet.

Yeah that sucks. You can add Ethernet for 30 bucks though.

poke01 · Monday at 2:18 PM

igor_kavinski said:
Apple is always welcome to increase the base price by 49% and see how that goes for them.

For that they to need hire Nvidia marketing people.

I agree with @johnsonwax, Apple rarely changes base pricing unless a major redesign happens. For example, the iPhone Pro price has remained the the same since 2017. Imagine Nvidia doing that with their GPUs.

poke01 · Monday at 2:21 PM

digitaldreamer said:
And, that iMac only has two Thunderbolt / USB 4 ports and no Ethernet.

The base iMac is a horrible value. In fact I don’t see the point in All in ones, they are useless once the display dies.

Eug · Monday at 2:22 PM

johnsonwax said:
Reminder that Apple designs to price points. The iMac is now 26 years of having ~$1299 base price (a 49% discount factoring for inflation). Apples pricing, particularly upgrades have no relationship to component costs, but to perceived value to the customer - just like in every other industry. I'm sure there are people walking into the car dealership who know the component costs of a trim upgrade, but no normal car buyer is aware of that and that bears no real relationship to how we buy things. Only the tech industry remains fixated on this from a long history of building PCs from components, but hardly anyone does that now. Even the gamer market has not only SKUs to pick from, but whole OEMs that cater to them.

poke01 said:
I agree with @johnsonwax, Apple rarely changes base pricing unless a major redesign happens. For example, the iPhone Pro price has remained the the same since 2017. Imagine Nvidia doing that with their GPUs.

Apple lowered the pricing with the M2 Mac mini.

That surprised me actually, as I had purchased a used M1 Mac mini a few months before, partially based on the belief the pricing tiers for M2 would be kept the same.

Doug S · Monday at 2:34 PM

Eug said:
Binned by CPU efficiency cores and GPU. CPU performance cores the same.

Can't be getting much yield increase by binning off two efficiency cores lol! This is mostly marketing binning - they would hardly recover enough SoCs that are fully functional other than basically a couple of GPU cores to make this worthwhile, almost all M4s sold with 8/8 CPU/GPU cores will have all 10 functional. If they cut out one of the big cores, a couple NPU cores, a TB controller and a memory controller they'd have enough of a yield difference to truly support it as a the base SKU but they don't want to handicap it that badly. No one is going to miss two E cores, the two missing GPU cores are all you'd notice.

It is interesting that they've dropped ethernet, but they probably have pretty good metrics on what people are using in existing iMacs. If almost everyone is using wifi as I would guess then making it a cheap (for Apple) $30 add on or letting people use a TB/USB ethernet adapter must have been needed to hit their target BOM for the $1299 list price.

Eug · Monday at 2:45 PM

Doug S said:
It is interesting that they've dropped ethernet, but they probably have pretty good metrics on what people are using in existing iMacs. If almost everyone is using wifi as I would guess then making it a cheap (for Apple) $30 add on or letting people use a TB/USB ethernet adapter must have been needed to hit their target BOM for the $1299 list price.

The base M3 iMac didn't have Ethernet either. And the reason they can add it for $30 is because it's actually located on the AC adapter.

IOW, none of the Apple Silicon iMacs have Ethernet on the machine. The Ethernet depends upon which AC adapter you get. BTW, AFAIK you can't buy that Ethernet AC adapter separately but most people would just get a USB hub with Ethernet adapter or something like that.

name99 · Monday at 2:52 PM

mvprod123 said:
New M4 tech specs from Apple. I don't remember Apple describing its microarchitecture in such detail.
View attachment 110453
View attachment 110454

Hmm. Most of that is obvious.
I assume the improved branch prediction is the special handling of branches that (almost) never change direction (eg test for error), and the faster return stack handling.
Next-gen ML accelerators is obviously the SME stuff which, apart from now being "developer-accessible" has at least one new feature, namely the ZA register transpose stuff.
Lower latency vector FP (for E-core) probably means using the same latency tweaks for an FMA that's only add, no multiply, that was given to the P-core in, what, M2 I think.

The one that's not obvious is WIDER vector FP. Anyone know what that's about? The most obvious guess is that prior to M4 (and A18?) the E-core double pumped NEON through a 64b wide execution unit, rather than having a full 128b wide execution unit. But I'm unaware that anyone has ever made such a claim, and you'd figure it would have been noticed by now by someone exploring around.

I THINK the GPU scheduling stuff refers to https://patents.google.com/patent/US20240272940A1
This is a large patent, and some of it is only relevant to the M Ultra. But the elements that are relevant to smaller machines include:
- in the past a kick (think "piece of a kernel") could only be scheduled to one core or all the cores in an SoC (or as third option, all cores of an Ultra). Now a kick can be scheduled to say 6 of 10 available cores. This seems obvious, but for it to be worthwhile you need some less obvious infrastructure in the compiler and elsewhere so that you can generate accurate estimate of how many cores makes sense for each kick.
- kicks can be scheduled onto cores one core at a time as they become available, rather than requiring all the cores used by the kick to be free at once
- scheduling queues have been virtualized to live in address space (ie "in RAM", but practically this probably means in L2). This is the next step in virtualization after virtualizing registers and threadblock scratchpad memory, with the same advantages -- rather than being limited by the previous fixed size of kick scheduling queues, now the runtime can create as many queues as large as makes sense.
- handling the end of a kick (either naturally, or context-switched out, or killed) has also been moved to virtualized queues. I assume this means that the immediate work of handling the end of the kick consists only of moving the kick to one of these queues. Then later work (releasing resources and such like) can be done by the companion core when it's not scheduling kicks, ie it can be deferred to when convenient rather than having to be done right away at the expense of more urgent work
- kicks can be schedule by deadline first, rather than just the previous models of priority and round-robin

name99 · Monday at 2:57 PM

johnsonwax said:
Maybe. That's an odd bit of support to add to the base M4 unless it was so cheap to implement there was no point excluding it. Even then, it would seem more likely for Apple to keep it in and never certify it or enable it via software because that's such an obvious upsell to Pro feature. Depending on how small the new Mini form factor is, they might be trying to grab a bit of the high end display-focused market (medical imaging stations, kiosks, etc.) The mini has always been part of the home theater scene.

You say 8K, I say 2*6K.
Now why would you want to send out a dual 6K signal to a single device?
Uhhhh...

naukkis · Monday at 2:59 PM

name99 said:
The one that's not obvious is WIDER vector FP. Anyone know what that's about? The most obvious guess is that prior to M4 (and A18?) the E-core double pumped NEON through a 64b wide execution unit, rather than having a full 128b wide execution unit. But I'm unaware that anyone has ever made such a claim, and you'd figure it would have been noticed by now by someone exploring around.

They added third Neon-pipeline thus made fp unit "wider".

name99 · Monday at 3:00 PM

poke01 said:
The base iMac is a horrible value. In fact I don’t see the point in All in ones, they are useless once the display dies.

Then don't buy one! Is that hard to understand?

The base iMac is a perfect machine for schools, and they will sell plenty of them to that market.

name99 · Monday at 3:01 PM

naukkis said:
They added third Neon-pipeline thus made fp unit "wider".

Really, that's the language they're using for that?
I kinda get it if you want to make a one-line bullet-point, but I think they could have done better.

Eug · Monday at 3:01 PM

Interestingly, the Thunderbolt ports no longer have the lightning bolt logo. They're just unlabelled, I guess because it no longer has non-Thunderbolt USB-C ports. I wonder if going forward this will be true of all new Macs. ie. Will the 5-port M4 Pro Mac mini have 5 Thunderbolt 4 ports?

BTW, here is the iMac announcement video:

smalM · Monday at 6:44 PM

naukkis said:
They added third Neon-pipeline thus made fp unit "wider".

That was the A17/M3 generation

The Hardcard · Monday at 6:53 PM

smalM said:
That was the A17/M3 generation

For the M3 series, only the M3 Max got the third FP pipeline. It’s new for the base M and the Pro.

FlameTail · Monday at 9:03 PM

mvprod123 said:
View attachment 110454

This slide confirms that M4's GPU has the same 2x RT improvement they advertised for A18 Pro.

Eug · Monday at 10:20 PM

Oops. Premature specification, from Amazon USA:

M4 Pro is 14-core CPU / 20-core GPU / 64 GB RAM with two front USB-C ports

(M3 Pro is 12-core CPU / 18-core GPU / 36 GB RAM)

Doug S · Monday at 11:07 PM

Eug said:
The base M3 iMac didn't have Ethernet either. And the reason they can add it for $30 is because it's actually located on the AC adapter.

IOW, none of the Apple Silicon iMacs have Ethernet on the machine. The Ethernet depends upon which AC adapter you get. BTW, AFAIK you can't buy that Ethernet AC adapter separately but most people would just get a USB hub with Ethernet adapter or something like that.

For a moment I was thinking "WTF" who puts an ethernet jack on a power cord but that's actually very Apple. One less wire connecting to your Mac is exactly what you'd expect them to want. You can take Jony Ive out of Apple, and get rid of cases where he went too far like the butterfly keyboard and having too few ports, but the minimalist ethos remains.

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