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

[chars1ub0w]

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).

This is evidence the M series has outgrown the MacBook Pro chassis introduced with the original M1 edition.
We know a redesign is coming.
We also know the current chassis does not implement the latest cooling tech used in the iPhone.
So, rather than leaving unused compute on the table, I think it's better to skip the stopgap M5 generation.

 

[Alameda]

This is evidence the M series has outgrown the MacBook Pro chassis introduced with the original M1 edition.
We know a redesign is coming.
We also know the current chassis does not implement the latest cooling tech used in the iPhone.
So, rather than leaving unused compute on the table, I think it's better to skip the stopgap M5 generation.

And we know a redesign is coming after than. And we know an M7 is coming after the M6. And we know that an M8 is coming after the M7. And on and on.

 

[chars1ub0w]

And we know a redesign is coming after than. And we know an M7 is coming after the M6. And we know that an M8 is coming after the M7. And on and on.

No, you don't understand my point. M1-M5 used the same MacBook Pro chassis/cooling. M6 will use a different one.

 

[conmee]

No, you don't understand my point. M1-M5 used the same MacBook Pro chassis/cooling. M6 will use a different one.

It will be interesting to see. If you are correct that the M-series has outgrown the chassis, how is that going to work with the rumored thinner design for the upcoming redesign? Do you think the M6 will run cooler/require less thermal headroom than the current M5? Unless there is a significant bump in performance due to 2nm which allows Apple to dial down the GHz, then I'm not sure the M6 will be any better off unless the chassis is bigger than the current chassis, or some other cooling magic is introduced.

 

[chars1ub0w]

I'm not sure the M6 will be any better off unless the chassis is bigger than the current chassis, or some other cooling magic is introduced.

They could put this tech in. The iPhone 17 Pro already has it. Apple says:
“Deionized water is sealed inside the vapor chamber, which is laser-welded into the aluminum chassis. This efficiently moves heat away from the components, allowing for higher sustained performance. The vapor chamber directs heat strategically through the system, where it is efficiently dissipated and released by the forged aluminum unibody.”

 

[Bungaree.Chubbins]

This is evidence the M series has outgrown the MacBook Pro chassis introduced with the original M1 edition.
We know a redesign is coming.
We also know the current chassis does not implement the latest cooling tech used in the iPhone.
So, rather than leaving unused compute on the table, I think it's better to skip the stopgap M5 generation.

Vapour chambers aren't some magical new golden bullet for cooling! Is there enough heatsink, is there enough airflow? Maybe a vapour chamber will help spread the heat out to a wide, thin heatsink better, but a slimmer laptop is going to have less total capacity for cooling, not more. If Apple wants to improve cooling, they can choose better fan speed curves, and not wait until a chip hits 100ºC to really ramp up the fans. Get them spinning before the chip is too hot, and you can dissipate the heat better.

 

[chars1ub0w]

If Apple wants to improve cooling, they can choose better fan speed curves, and not wait until a chip hits 100ºC to really ramp up the fans. Get them spinning before the chip is too hot, and you can dissipate the heat better.

You can already control fan speed. Before hitting the return button to start the run, you can hit the cooling symbol for fan speed ahead of time.

 

[uller6]

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.

This is the way to high yields! If there is highest probability of one CPU defect, just fuse off 1 core in each cluster to insulate you from 1-3 bad cores.