With Turbo Boost disabled, is the 2.6 GHz i7 faster than the 2.3 GHz i9 in single-thread applications?

[joseph.s.jones]

Hi folks,

I spend most of my time away from home using single-thread applications, and I plan on disabling Turbo Boost to keep a cooler, quieter and overall more power-efficient laptop. The i7 may be a no-brainer with this use case, but I'd like to have the extra two cores of the i9 at my disposal on the rarer occasions that I use multi-threaded applications (especially given the small price increase between i7 and i9). My workflow may also change in the future. I'd like to buy the 2.3 GHz i9 but will this actually negatively impact me vs the 2.6 GHz i7 for my current workflow?

• Both CPUs are 9th gen, so I imagine the 2.6 GHz i7 would beat the 2.3 GHz i9 in single-thread applications without Turbo Boost (due to the higher base clock of the i7) is this the case? I.e. is each core of the i9 the same as each core on the i7 but the i9 cores are slightly underclocked and therefore individually less powerful at base clock speeds?
• Or is a single lower clocked core of the i9 in some way better or able to achieve the same performance as a single core of the higher clocked i7? I see the i9 has more level 3 cache than the i7 for example, I don't know what impact this has?
• Will a single-thread application still manage to use all of the cores in some way, making the i9 always the better choice?

Thanks for your help and apologies for my limited understanding of how modern CPUs work. It was clearer a decade ago when more GHz was most often better.

 

[LinkRS]

Hi folks,

I spend most of my time away from home using single-thread applications, and I plan on disabling Turbo Boost to keep a cooler, quieter and overall more power-efficient laptop. The i7 may be a no-brainer with this use case, but I'd like to have the extra two cores of the i9 at my disposal on the rarer occasions that I use multi-threaded applications (especially given the small price increase between i7 and i9). My workflow may also change in the future. I'd like to buy the 2.3 GHz i9 but will this actually negatively impact me vs the 2.6 GHz i7 for my current workflow?

• Both CPUs are 9th gen, so I imagine the 2.6 GHz i7 would beat the 2.3 GHz i9 in single-thread applications without Turbo Boost (due to the higher base clock of the i7) is this the case? I.e. is each core of the i9 the same as each core on the i7 but the i9 cores are slightly underclocked and therefore individually less powerful at base clock speeds?
• Or is a single lower clocked core of the i9 in some way better or able to achieve the same performance as a single core of the higher clocked i7? I see the i9 has more level 3 cache than the i7 for example, I don't know what impact this has?
• Will a single-thread application still manage to use all of the cores in some way, making the i9 always the better choice?

Thanks for your help and apologies for my limited understanding of how modern CPUs work. It was clearer a decade ago when more GHz was most often better.

Howdy joseph.s.jones,

Logic would dictate that if you locked your CPU to its non Turbo speed, the i7 would be ~12% faster when using single threaded apps. However, this is not as common as you might think. Some things are inherently single threaded, but macOS is not, and many programs (including Chrome) that do spawn single threaded tasks, will spawn multiple single threaded (or background if you prefer) tasks. In those cases, unless the particular app only uses 6 or fewer threads, the i7 would lose its advantage due to having fewer threads to play with.

I have had my new 16" MacBook Pro for 17 days now, and waffled over getting the base i7 over the i9, for the same reason you are discussing. Thinking that in lightly threaded apps, the i7 would be a better performer (I did not, ,and am not considering disabling turbo boost). What turned me around were two things. First the GeekBench scores. The i9 outperforms the i7 in single core scores, and in multi-core (duh LOL). Secondly was the cost. When I took the base i7 (using my Vet discount), and upgraded it to the 1 TB SSD, and the 8 GB 5500M, the cost difference from the base i 9 was exactly $0 ($2519). Granted, the base only had the 4 GB 5500M, but that was only a $90 upgrade, so the difference in cost between them was $90 ($2609 if anybody cares, normal base price is $2799). So I thought it was worth $90 more for the i9, and went with it. However, now we have the ridiculously expensive option of the 5600M for a "measly" $630 more (Vet price), taking the total $3149. Nope, can't justify that.....

I would suggest (and encourage) you to try whichever model you choose without disabling turbo first. The Intel CPUs are designed (particularly the mobile ones) to change its clock based on workload. If you aren't pushing it, it shouldn't throttle up, and when it does throttle up, you will get your workload completed that much faster, essentially saving battery life (less time running, spin up for a few clocks, and then goes right back down). If you think it will work better with it off, then try it with it off and see how it works for your personal usage. You might be pleasantly surprised .

Good luck!

Rich S.

 

[joseph.s.jones]

This was a really helpful reply, thank you very much Rich.