Question Multi Threading on Apple Firestorm ?

FlameTail

Member
Dec 15, 2021
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Apple Firestorm core in the M1 does not have Simultaneous Multi Threading. I was wondering, [1] What effect will be there if SMT is implemented to a future successor of the Firestorm ?

Obviously, it seems that the Firestorm core has not been designed for SMT to work optimally. The Firestorm core already uses OoOE ( Out of Order Execution ), and is based on ARM ( compared to Intel on x86 ).

[2] So will there be the same level of benefit that is obtained by implementing SMT on an Intel core, if SMT is added to Firestorm ( or a future successor of it )?
 

scannall

Golden Member
Jan 1, 2012
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Apple Firestorm core in the M1 does not have Simultaneous Multi Threading. I was wondering, [1] What effect will be there if SMT is implemented to a future successor of the Firestorm ?

Obviously, it seems that the Firestorm core has not been designed for SMT to work optimally. The Firestorm core already uses OoOE ( Out of Order Execution ), and is based on ARM ( compared to Intel on x86 ).

[2] So will there be the same level of benefit that is obtained by implementing SMT on an Intel core, if SMT is added to Firestorm ( or a future successor of it )?
As wide as the Apple cores are, and as much memory bandwidth as they have I'm not sure you'd get much of an uplift. And it would introduce another attack vector for hackers to try and get through.
 
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Ajay

Lifer
Jan 8, 2001
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As wide as the Apple cores are, and as much memory bandwidth as they have I'm not sure you'd get much of an uplift. And it would introduce another attack vector for hackers to try and get through.
Agreed, Apple has taken the approach of maximizing ILP above all (would like to see a good breakdown of the XCode compiler optimizations). I haven't read about it, but I wouldn't be surprised if they have an industry leading branch predictor and prefetcher. SMT just doesn't fit with Apple's design philosophy.
 

Doug S

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Feb 8, 2020
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The argument for implementing SMT - which was already extremely weak for a phone or standard consumer laptops like a Macbook Air - became a lot worse when the security issues around it were discovered. Even if Apple had considered implementing SMT that might have caused them to change their mind, and with good reason.
 

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