What's Different between 15-Core and 18-Core Pro CPUs?

[Alameda]

Please read carefully...

The M5 Pro CPU's come in two flavors:

• 15-Core CPU with 16-Core GPU
• 18-Core CPU with 20-Core GPU

These use the same dies, don't they? Does anyone know what is different between these two? Do they simply lock out 3 CPUs and 4 GPU's in the lower-cost model? Are they packaged differently, or is it just a software lock? Is the 15-Core built from dies which fail die test and then specific cores are locked out?

Thank you.

 

[maflynn]

Does anyone know what is different between these two?

One has 3 more CPU cores and 4 GPU cores then the other.

 

[Alameda]

One has 3 more CPU cores and 4 GPU cores then the other.

I think you did not understand the question.

 

[maflynn]

I think you did not understand the question.

The title states whats the difference between the two, and I'm giving it you - one will be faster then the other

I know I'm being pedantic, but overall, does it matter given that one will be faster then the other and people will choose what best fits their needs. Its not like we'll suddenly gain access to those extra cores if we chose the lower cost one

 

[leman]

Please read carefully...

The M5 Pro CPU's come in two flavors:

• 15-Core CPU with 16-Core GPU
• 18-Core CPU with 20-Core GPU

These use the same dies, don't they? Does anyone know what is different between these two? Do they simply lock out 3 CPUs and 4 GPU's in the lower-cost model? Are they packaged differently, or is it just a software lock? Is the 15-Core built from dies which fail die test and then specific cores are locked out?

Thank you.

They disable a bunch of cores, likely by fusing them of. It’s possible that the dies fail some tests (or that the binned dies consume more power than un-binned ones, for example, power-binning is apparently common in mobile), we just don’t know.

The CPU is arranged in three clusters of six cores (one prime-core cluster and two medium-core clusters), so it is my understanding that the the 15-core model disables one core per cluster.

 

[JPack]

We don't know - might be purely marketing and cores disabled to create a product stack only. Or could be genuinely defective cores.

M5 starts at $1,699. The M5 Pro 15/16-core is $2,199. Without it, the M5 Pro would start at $2,399 which is a huge jump for customers wanting just a bit more power.

 

[JulianL]

We don't know - might be purely marketing and cores disabled to create a product stack only. Or could be genuinely defective cores.

...

Or a combination of the two. As you say, we don't know, but if at any point in the product lifecycle the failure rate on perfect 18C/20G dies was sufficiently low such that there weren't enough partially faulty dies to fulfil the 15C/16G M5 product demand at that time then my guess is that Apple wouldn't allow a product drought to happen on those products but would rather make up the shortfall in 15C/16G dies by deliberately disabling some 3 CPU cores and 4 GPU cores on perfectly good 18C/20G dies.

If the above ever happened then the answer to Alameda's question would be that the 15C/16G part is not necessarily a single thing - at any given point in time some might be fully functional 18C/20G dies with 3 x CPU cores and 4 x GPU cores deliberately disabled and others might be dies where some of the cores did genuinely fail quality assurance so could never have gone into a 18C/20G product.

It also seems likely to me that within an individual die there might well be a mixture. It's pretty inconceivable to me that there would be enough dies with a "perfect" failure rate such that exactly 1 CPU core in each block of 6 and 4 GPU cores are faulty so there are probably also M5 15C/16G parts out there where maybe there are 2 faulty CPU cores disabled plus one good one intentionally disabled and similarly some mix of genuinely faulty GPU cores disabled and intentionally disabled good GPU cores in it to get to the right core count for a 15C/16G part.

 

[chars1ub0w]

We don't know - might be purely marketing and cores disabled to create a product stack only. Or could be genuinely defective cores.

M5 starts at $1,699. The M5 Pro 15/16-core is $2,199. Without it, the M5 Pro would start at $2,399 which is a huge jump for customers wanting just a bit more power.

On the other hand, the difference between the two Pro chips is only $200, and likely just a single digit percentage of the total price. I'd be surprised if someone in the market for such an expensive system desperately needed to save that $200. Although they can certainly fuse off something in each perfectly-good core cluster, it makes sense if they are defective ones.

 

[JPack]

On the other hand, the difference between the two Pro chips is only $200, and likely just a single digit percentage of the total price. I'd be surprised if someone in the market for such an expensive system desperately needed to save that $200. Although they can certainly fuse off something in each perfectly-good core cluster, it makes sense if they are defective ones.

View attachment 2614838

Many people don't look at it that way though. The 15/16-core version is the minimum entry point to the M5 Pro chip. If they don't need the additional power of 18/20-core, then why spend it?

$2,149 is also within throwing distance of $1,999. And these will undoubted be on sale with $150 off.

If 15/16-core was really binned from defective chips, it should be available in 16-inch MBP as well. The lack of that option suggests Apple merely trying to close the price gap between M5 and M5 Pro for 14-inch because many can be encouraged to spend $2k.

 

[Alameda]

On the other hand, the difference between the two Pro chips is only $200, and likely just a single digit percentage of the total price. I'd be surprised if someone in the market for such an expensive system desperately needed to save that $200. Although they can certainly fuse off something in each perfectly-good core cluster, it makes sense if they are defective ones.

View attachment 2614838

Hypothetically, IF:
A) The 15/16-core chip merely contained ID code indicating to the firmware to use only 15/16 cores, and if
B) There was a software hack that tricked the system into believing the 18/20 core chip was installed, and if
C) You ran a series of tests to determine that all 18/20 cores were working correctly, THEN

You converted your 15/16 machine into an 18/20 core machine...
Which would be pretty doggone cool.

 

[JPack]

Hypothetically, IF:
A) The 15/16-core chip merely contained ID code indicating to the firmware to use only 15/16 cores, and if
B) There was a software hack that tricked the system into believing the 18/20 core chip was installed, and if
C) You ran a series of tests to determine that all 18/20 cores were working correctly, THEN

You converted your 15/16 machine into an 18/20 core machine...
Which would be pretty doggone cool.

The configuration is fused in the SoC. Even the RAM config is. Recall iPad Pro M4 teardowns clearly showed 12GB RAM chips. Apple marketed it with 8GB and nobody could enable 12GB.

 

[conmee]

I'm leaning toward the 15/16 was offered on purpose. Is there a reason binned can't come in other combinations... 14/18, 12/12, 16/16 etc? Would seem to me that the manufacturing process would allow for a variety of combinations (hence, Intel has a million SKUs). Unless 15/16 was a frequent manufacturing defect that allows Apple to stock it and fulfill orders, I'm thinking cores are either disabled or manufactured as 15/16 on purpose.

 

[leman]

I'm leaning toward the 15/16 was offered on purpose. Is there a reason binned can't come in other combinations... 14/18, 12/12, 16/16 etc? Would seem to me that the manufacturing process would allow for a variety of combinations (hence, Intel has a million SKUs). Unless 15/16 was a frequent manufacturing defect that allows Apple to stock it and fulfill orders, I'm thinking cores are either disabled or manufactured as 15/16 on purpose.

Manufactured defects of that kind are extremely unlikely - the stars need to align in a spectacular fashion to create defects in exactly one core from each cluster and nowhere else.

The chips are likely fully functional, and fusing off the cores in this specific pattern is almost exclusively done to create product differentiation and increase profits. That’s pretty much it.

Another remote possibility is that at least some binned chips have higher than expected power consumption than designed (other kind of defect) and that the fusing brings it down to nominal again.

 

[chris11]

Interesting discussion...

I'm upgrading from a "binned" M2 Pro 14'' and have just ordered the "binned" M5 Pro 14''.

Here's my chain of thought...

I really like the 14'' form factor and value the fact my M2 Pro is perfectly quiet and doesn't heat up (still suffering from my i9 trauma I guess 🙂.

I had been pondering for a long time whether to choose the M5, M5 Pro 15 core or M5 Pro 18 core. I really don't need the GPU power of the Max.

One thing Apple does to segment them is memory: the M5 has max 32 GB, the 15 core M5 Pro has max 48 GB and the 18 core M5 Pro has max 64 GB. My M2 Pro had already 32 GB, I wanted to upgrade, so that ruled out the M5. At this point options left were:

- M5 Pro 15 core, 48 GB
- M5 Pro 18 core, 48 GB
- M5 Pro 18 core, 64 GB

Now I noticed that for M5 Pro 15 core 48 GB the online Apple store (Italy) offers a choice between the 70W power brick and the 96 W one.

However, for the M5 Pro 18 core choices, only the 96 W one can be selected. My M2 Pro came with a 67 W power supply. So somehow my overheating-i9 trauma flared up again. I (maybe irrationally) feel happier knowing my 14'' can dissipate those 67 W already so 70 W shouldn't be a problem in the same kind of chassis.

Also, for the M5 Pro 18 core the FOMA to not go the full way to 64 GB is kicking in... Those + 3 cores and + 24 GB RAM end up being + 450 EUR. Paying more for something not really needed and risking worse fan noise / heat was tipping the needle to the M5 Pro 18 15 core, 48 GB in the end.

Of course we're MacRumors forum users so we way over-think these things, I guess 🙂

-- Chris

 

[rb2112]

The 15/16-core version is the minimum entry point to the M5 Pro chip. If they don't need the additional power of 18/20-core, then why spend it?

Nowadays, this is how I think about spending on a MBP. In the past it was "why not max it out?"

If 15/16-core was really binned from defective chips, it should be available in 16-inch MBP as well.

You'd think, but not necessarily. Maybe Apple analysis shows enough buyers of the 16 inch make it worth not offering the lower config (from a production/stocking/selling perspective), who knows. Or maybe it's part of their attempt to not confuse the sales page. 3rd, could be part of the recent "base model increased configs' optioning (you have to buy 1TB vs 512), now you have to buy 18 core vs 15 core for the 16 inch.

 

[chars1ub0w]

One thing Apple does to segment them is memory: the M5 has max 32 GB, the 15 core M5 Pro has max 48 GB and the 18 core M5 Pro has max 64 GB. My M2 Pro had already 32 GB, I wanted to upgrade, so that ruled out the M5.

That's a really good point. One way to approach it is to figure out how much Unified RAM you'll be comfortable with. Based on this, looking at the store, it seems there is a huge gap for going from Pro to Max. If I have things correct, it seems like the base M5 Max with 36GB RAM is quite an odd-ball. So basically, the penalty for going from Pro to Max is effectively $1500.

$1699

M5 10 CPU cores 10 GPU cores 16GB (opt. 24/32GB)

+$500

M5 Pro 15 CPU cores 16 GPU cores 24GB (opt. 48GB)

+$200

M5 Pro 18 CPU cores 20 GPU cores 24GB (opt. 48GB/64GB)

+$1200

M5 Max 18 CPU cores 32 GPU cores 36GB

+$300

M5 Max 18 CPU cores 40 GPU cores 48GB (opt. 64GB/128GB)

 

[Plutonius]

The difference is 3 CPU Cores and 4 GPU Cores 🙂.

 

[JulianL]

There's a another difference that no one has discussed that might actually be a big deal for some people and it's related to standard configurations vs built-to-order systems.

The data below is data from today. It's UK data but in general you just change UK Pounds (£) to US Dollars ($) to get the conversion to US pricing (US $ prices not including sales tax whereas UK £ prices do include tax).

Here's the Apple pricing for a few 14" M5 Pro systems all with 24GB of memory ...

M5 Pro 15C/16G 1TB SSD - £2,199
M5 Pro 15C/20G 2TB SSD - £2,599
M5 Pro 18C/20G 1TB SSD - £2,399
M5 Pro 18C/16G 2TB SSD - £2,799

So, just the standard extra £400 ($400 in the USA) to upgrade from a 1TB to a 2TB SSD and an extra £200/$200 to upgrade from an M5 Pro 15C/16G to an M5 Pro 18C/20G. Nothing to see here.

But, for the 15C/16G M5 Pro model the standard build comes with a 1TB SSD whereas the 18C/20G M5 Pro standard build comes with a 2TB SSD. Again, not very interesting until you look at the sort of discounts you can get even the week after launch via third-party retailers such as Amazon.

Here's the pricing on Amazon UK right now for the 14" M5 Pro MacBook Pro standard builds/configurations (rounded up to the nearest £1)...

M5 Pro 15C/16G 1TB SSD - £2,014
M5 Pro 18C/16G 2TB SSD - £2,558

So now lets look at a couple of buyer situations....

1 - You only need a 1TB SSD and while you're not a power user you're thinking that for that extra £200 you might as well get the higher performance 18C/20G M5 Pro model just for a bit of future proofing. Well, fair enough but because that 1TB SSD is a standard configuration for the lower performance 15C/16G M5 Pro but not for the more performant M5 Pro version then if you were to drop down to that lower spec 15C/16G M5 Pro you could buy your MacBook via Amazon UK (or another reputable reseller) and actually save £385 just for dropping the 3 CPU cores & 4 GPU cores that you might never really need. You might still go for the higher performance M5 Pro version but it changes the thinking from "it's only an extra £200" to "in practice it's actually an extra £385" to get those extra cores.

2 - You want (or need) a 2TB SSD but you know you won't be doing really heavy workloads so are perfectly OK with a 15C/16G M5 Pro. (I confess that what comes next was a surprise to me.) If you stick to your plan then (as far as I'm aware) you'll have to buy direct from Apple since a 15C/16G M5 Pro with a 2TB SSD is not a standard configuration so you'll end up paying an extra £400 to up-spec the basic 15C/16G M5 Pro model from a 1TB to a 2TB SSD and end up paying Apple £2,599 for your MacBook. If however you decided to go for the more performant 18C/20G M5 Pro model you now get the 2TB SSD in the standard configuration so you can go and buy that from Amazon UK for £2,558. By increasing the CPU spec from 15C/16G to 18C/20G you actually end up saving £41!

So, depending on what size SSD you want, how that maps to the standard configurations for the 2 versions of the M5 Pro chip, and how the third-party discounts on the standard configurations evolve or stay the same over time your choice of 15C/16G M5 Pro or 18C/20G M5 Pro in your MacBook Pro might have quite a significant effect on the overall system price - more than you might think by just looking at Apple pricing and with (at least for now in the UK) that (weird to me) anomaly where getting the more performant M5 Pro version actually reduces the overall system price.

 

[conmee]

That's a really good point. One way to approach it is to figure out how much Unified RAM you'll be comfortable with. Based on this, looking at the store, it seems there is a huge gap for going from Pro to Max. If I have things correct, it seems like the base M5 Max with 36GB RAM is quite an odd-ball. So basically, the penalty for going from Pro to Max is effectively $1500.

$1699

M5 10 CPU cores 10 GPU cores 16GB (opt. 24/32GB)

+$500

M5 Pro 15 CPU cores 16 GPU cores 24GB (opt. 48GB)

+$200

M5 Pro 18 CPU cores 20 GPU cores 24GB (opt. 48GB/64GB)

+$1200

M5 Max 18 CPU cores 32 GPU cores 36GB

+$300

M5 Max 18 CPU cores 40 GPU cores 48GB (opt. 64GB/128GB)

I always prioritize screen size, then maximum memory, then maximum storage (for my needs), and then the least expensive CPU that I must buy to get all of it. This put me in M5 Pro 18/20 + 64GB territory. I could probably get by just fine with M5 + 32GB option but they don't offer that in a 16" MBP and I just can't go back to a smaller screen.

 

[chars1ub0w]

2 - You want (or need) a 2TB SSD but you know you won't be doing really heavy workloads so are perfectly OK with a 15C/16G M5 Pro. (I confess that what comes next was a surprise to me.) If you stick to your plan then (as far as I'm aware) you'll have to buy direct from Apple since a 15C/16G M5 Pro with a 2TB SSD is not a standard configuration so you'll end up paying an extra £400 to up-spec the basic 15C/16G M5 Pro model from a 1TB to a 2TB SSD and end up paying Apple £2,599 for your MacBook. If however you decided to go for the more performant 18C/20G M5 Pro model you now get the 2TB SSD in the standard configuration so you can go and buy that from Amazon UK for £2,558. By increasing the CPU spec from 15C/16G to 18C/20G you actually end up saving £41!

I don't see an anomaly in the USA.

Amazon USA vs. Apple store:
$2549/$2599 M5 Pro 15 CPU cores 16 GPU cores 24GB 2TB
$2749/$2799 M5 Pro 18 CPU cores 20 GPU cores 24GB 2TB

 

[deconstruct60]

If I have things correct, it seems like the base M5 Max with 36GB RAM is quite an odd-ball. So basically, the penalty for going from Pro to Max is effectively $1500.

...

+$1200

M5 Max 18 CPU cores 32 GPU cores 36GB

+$300

M5 Max 18 CPU cores 40 GPU cores 48GB (opt. 64GB/128GB)

The memory on the 32 GPU core model isn't 'odd' as much as it is missing a memory controller ( probably also binned down) . It is not only CPU and GPU cores that get impacted by chip fabrication defects. There are other single points of failure that could get a die tossed even if no CPU/GPU core defects.

The memory bandwidth is 460GB/s were as full GPU is 614GB/s. ( the M5 Pro having 307GB/s ). Fewer memory packages, less concurrent memory traffic. So 3x12GB = 36GB and 4x12GB = 48GB. They are by-passing 3x16GB = 48GB because hoping folks will 'upshift' to the full (higher margin) GPU to get there. And two ways to get to 48GB is a bit more confusing build-to-order selection picker. The 3x32GB = 96GB path is just likely not going to be chosen by many ( using the 4x32GB = 128GB memory parts). Most folks who have that much base memory requirements and can afford those prices, likely want more compute to process it with.

More memory packages you have to buy the more the base level price jumps up. 3 packages is more affordable than 4. Especially, at the prices that Apple charges.

The binned Max becomes something that is incrementally better than a Pro but doesn't stretch the budget quite as far. It is also probably a better 'fit' to the 14" model also. (a little less max thermals when pushed hard for long periods, but better performance than the M5 Pro options.)


P.S. The Pro GPU chiplet is substantially smaller and have much fewer memory controllers. Going from 2 to 1 is a bigger negative impact than going from 4 to 3. Also the chip costs less so easier to take the hit on leaving more on the discard pile if getting a high enough price was what is still being sold for money.

 

[JulianL]

I don't see an anomaly in the USA.

Amazon USA vs. Apple store:
$2549/$2599 M5 Pro 15 CPU cores 16 GPU cores 24GB 2TB
$2749/$2799 M5 Pro 18 CPU cores 20 GPU cores 24GB 2TB

Disappointing for those in the USA. For once the UK gets a technology break that the USA doesn’t?

Sadly I’m travelling for another month otherwise I think I would jump on the 18C/20G 2TB deal. The only thing I’m slightly worried about is the thermals on the high end M5 Pro because I’ve read reports of the Max doing quite a lot of throttling in the 14” chassis. I’m actually more worried about the fans being more noticeable than I am about throttling because I don’t expect to do long duration high load stuff so I’m trying to search for info on fan noise/behaviour with the 14” 18C/20G M5 Pro but not finding much on that so far.

 

[deconstruct60]

Manufactured defects of that kind are extremely unlikely - the stars need to align in a spectacular fashion to create defects in exactly one core from each cluster and nowhere else.

The chips are likely fully functional, and fusing off the cores in this specific pattern is almost exclusively done to create product differentiation and increase profits. That’s pretty much it.

Exclusively for product differentiation is probably too extremely. It is a major contributor to where the prices are set. Nobody is going to wait for the defective bin to fill up so that they can sell the entry level product which is likely the highest unit volume. But it is incremental profits looking to gain.

It doesn't have to be one in each cluster. It can just be one in a single cluster and the other two are flipped off to make things symmetric. This issue is that don't have to go to extremes so fused on the absolute minimum broken area for any usage of 'fusing off'.

Similar issue if one of the Max GPU memory controllers is borked. Fuse off some CPU/GPU so that reduced bandwidth still leads to similar bandwidth balancing assumptions.

Another remote possibility is that at least some binned chips have higher than expected power consumption than designed (other kind of defect) and that the fusing brings it down to nominal again.

As wafer costs go up , only picking the most perfect of perfect gets more expensive to cover.

 

[chris11]

The only thing I’m slightly worried about is the thermals on the high end M5 Pro because I’ve read reports of the Max doing quite a lot of throttling in the 14” chassis. I’m actually more worried about the fans being more noticeable than I am about throttling because I don’t expect to do long duration high load stuff so I’m trying to search for info on fan noise/behaviour with the 14” 18C/20G M5 Pro but not finding much on that so far.

Yes, that was also my concern and one factor that let me order the 15 core M5 Pro in the end... Did you notice that when you order the 15 core version in the online store Apple let's you choose between the 70 W and 96 W power supplies? Instead, if you order the 18 core one, only the 96 W one can be selected. So there must be a difference in power consumption high enough for Apple to configure this differently. I find it remarkable the cut-off between the two choices is right between the two Pro versions (as opposed to more naturally between base and Pro/Max).

-- Chris

 

[SalisburySam]

What's Different between 15-Core and 18-Core Pro CPUs?​

$200 in your pocket for the 15-Core.
$200 in Apple’s pocket for the 18-Core.