CPU Turbo Boost - when?
by business_kid from LinuxQuestions.org on (#5B5Y6)
There's really 2 questions, and I'm interested in the smaller end of CPUs, i.e. 2/4/8 & just maybe 16 cores. Ampere Mt Snow servers come with an 80 core Arm CPU, but I'm not in that territory, or threadrippers either.
1. When does boost turn on? When 1 core is busy? Does it need more that one thread under load? And how is 'under load' defined? I am presuming 'boost mode' keeps a watchful eye on the thermals.
2. When does boost turn off? I presume overheating and load are factors. I interestingly came across Ampere Computing's specs for it's machine which quoted only it's boost speed as a cpu frequency, because it had the cooling to guarantee thermal issues would not drive you out of turbo. But how fine things are cut would be interesting.
My sucky cpu has no boost, but it did show me the perfect way to get boost to cut out Code:mksquashfs <some backup dir> On my 2 core/4 thread i3, top showed ~380%, whereas 'make -j <plenty>' and most things showed only 200%. Making a squashfs also played havoc with the cpu thermals.
It's actually an important question. Apple's M1 boasts 8 cores, 2.5Ghz with boost to 4.5 Ghz, and offers 50% faster compile times than previous Macbook Pros. My son has a previous Macbook Pro from his job, and that runs on an i7-9750H, 6 cores/12 threads, 2.6Ghz rising to 4.5Ghz on boost, and that's only 50% as fast. They're both 45W power disappation. So I guess doing 4.5Ghz is a lot more power hungry on the i7 than the M1, and the M1 can nearly live in boost, while the i7 can only make short infrequent visits.
So I conclude from the above, that improving cpu cooling gets you more boost, to the point where you can live there if you have the load?
1. When does boost turn on? When 1 core is busy? Does it need more that one thread under load? And how is 'under load' defined? I am presuming 'boost mode' keeps a watchful eye on the thermals.
2. When does boost turn off? I presume overheating and load are factors. I interestingly came across Ampere Computing's specs for it's machine which quoted only it's boost speed as a cpu frequency, because it had the cooling to guarantee thermal issues would not drive you out of turbo. But how fine things are cut would be interesting.
My sucky cpu has no boost, but it did show me the perfect way to get boost to cut out Code:mksquashfs <some backup dir> On my 2 core/4 thread i3, top showed ~380%, whereas 'make -j <plenty>' and most things showed only 200%. Making a squashfs also played havoc with the cpu thermals.
It's actually an important question. Apple's M1 boasts 8 cores, 2.5Ghz with boost to 4.5 Ghz, and offers 50% faster compile times than previous Macbook Pros. My son has a previous Macbook Pro from his job, and that runs on an i7-9750H, 6 cores/12 threads, 2.6Ghz rising to 4.5Ghz on boost, and that's only 50% as fast. They're both 45W power disappation. So I guess doing 4.5Ghz is a lot more power hungry on the i7 than the M1, and the M1 can nearly live in boost, while the i7 can only make short infrequent visits.
So I conclude from the above, that improving cpu cooling gets you more boost, to the point where you can live there if you have the load?