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What should the CPU usage be of a fully-loaded CPU that has been throttled?

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Re: What should the CPU usage be of a fully-loaded CPU that has been throttled?

#171

Post by bick_nyers »

bserge wrote: post #146
j605 wrote: post #144

Earlier quoted context omitted.

In extension to what the other commenter said, critical temperature that is listed is usually higher than the maximum operating temperature so it is safe to run at the maximum.

It is safe only because it throttles heavily . Shutdown temperature is just 5 degrees higher btw. At 100 the processor is at high risk of damage, which is why there's a built-in throttling mechanism. Just imo, if it was safe it would be running at full speed (or at least max base clock) at that temperature. As someone else said, they're made for burst operation these days, but again, that does not excuse manufacturer…

I personally run my hardware for longevity (larger PSU, good temperature ranges, minimal overclocking, etc.) and upgrade every two years but I migrate my tech. downwards. Example: Gaming Rig -> Misc. Project/Guest PC -> NAS/Media Box. Working in tech. you very often make a salary that allows you to upgrade all of these rigs every year with no real consequences, but I think if nothing else we should be trying to reduce tech. waste. Semiconductor manufacturing has a large carbon footprint just like everything else.

Re: What should the CPU usage be of a fully-loaded CPU that has been throttled?

#172

Post by deviledeggs »

Godel_unicode wrote: post #165
deviledeggs wrote: post #98

Earlier quoted context omitted.

IT overlap is mostly because computers and the internet are military technology. Mainframes, IC's and the transistor itself were bankrolled by US military money. The internet and GPS, the core technologies of our time, are both direct descendants of the US military. You may not like it, but the entire IT and tech field are built on US military tech

You're just picking a point in time and calling that the beginning; every one of those things is based on previous tech with no military background. Even if it were true that in the distant past a thing had a military application/funding, there's no reason to use their terms for new things which aren't military in nature. No commercial liner calls it's full speed "military power". It's just cosplay at this point.

If you go far enough back all of our technology arises from fire and the wheel.

There's plenty of room to debate how much of our technology came from the military, but I don't think naming is a big deal.

Take the word "screen" for example. The original meaning was a partition to protect from heat. Many of these were fabric, and led to "magic lantern" shows done with shadows. The word was repurposed again for the projection era. And yet again for tube TV's and beyond.

If you told somebody from 100 years ago to look at the screen they would have no idea what you're talking about because the original meaning is lost.

That's why I don't think it matters whether we use military terms for computer stuff. It doesn't have its original meaning anymore.

Re: What should the CPU usage be of a fully-loaded CPU that has been throttled?

#173

Post by CodeWriter23 »

concerned_user wrote: post #119
CodeWriter23 wrote: post #117

I think this article asks the wrong question. The correct question IMO is why is the frequency throttled instead of maxed out when a program is saturating the CPU?

If it is thermal throttling then it means cpu is maxed out for the given conditions.

I agree with that, but it seems like the use case specified is ordinary power conservation mode, not critical, thermally-induced power reduction mode.

And also, why are systems shipped with inadequate thermal control?

Re: What should the CPU usage be of a fully-loaded CPU that has been throttled?

#174

Post by SavantIdiot »

jeffbee wrote: post #170
SavantIdiot wrote: post #49

Earlier quoted context omitted.

True, I should have more accurately said: all large volume cloud vendors I worked with.

So, you've never used GCE, EC2, or Azure? Because they all offer frequency scaling.

Yes, I use them all the time. Did you see the part where I was talking about my customers?

Re: What should the CPU usage be of a fully-loaded CPU that has been throttled?

#175

Post by VortexDream »

annoyingnoob wrote: post #163
VortexDream wrote: post #108

Earlier quoted context omitted.

I fall in the 50% camp because showing 100% when it's clearly not using 100% of what the CPU is capable of is misleading, particularly in troubleshooting performance issues.

I think either 50% or 100% is misleading without more information. In either case you can be left wondering where your bottleneck might be and your first guess probably is not something like more cooling.

I think showing 100% is far worse, because then I have to rely on my subjective experience of the interface I'm working with to notice that something is wrong. 100% isn't just misleading, it's wrong on a UX level. At least when it shows 50%, I immediately have a sense of, "wait, that's wrong" and I can even begin troubleshooting and look at the current clockspeed, temperature, core usage, etc.

Re: What should the CPU usage be of a fully-loaded CPU that has been throttled?

#176

Post by brokenmachine »

bserge wrote: post #147
d110af5ccf wrote: post #136

Earlier quoted context omitted.

Counterpoint - during typical (consumer) usage hardware spends most of the time idle. Hardware capable of sustaining the maximum workload indefinitely is likely to have a lower maximum in practice. Unsustainable bursts are likely to provide higher overall performance for typical workloads, so it makes sense to optimize the hardware design for those.

I guess, but workstation class laptops still overheat, so again, piss poor design.

I'd be willing to bet that a "workstation class" laptop that had sufficient cooling to run continuous benchmarks without overheating would be quite unpopular in the market, because of the weight/size burden.

Re: What should the CPU usage be of a fully-loaded CPU that has been throttled?

#177

Post by omegalulw »

MauranKilom wrote: post #149

Fun tangential anecdote regarding how interconnected and unintuitive CPU performance can be: I once made something run 20% faster by spawning a thread that did nothing but spin (i.e. while (true); ). I was trying to optimize some FEM code, toying with (hardcoded) solver parameters. On one console I had it spitting out the wall clock durations of time steps as the simulation was running, while on the other I was prepa…

I'm confused, how is COU speed tied to memory? AFAIK, memory is tied to CPU base speed which is almost always 100 MHz. The CPU then just scales it's own multiplier.

Re: What should the CPU usage be of a fully-loaded CPU that has been throttled?

#178

Post by tayo42 »

waterhouse wrote: post #113
tayo42 wrote: post #106

Earlier quoted context omitted.

Yeah that would be the thing to prove that prime95 is going through more instructions so the cpu runs hotter

I see. But I expect that some instructions cost more (i.e. generate more heat) than others. Someone mentions AVX instructions, for example; presumably 1 million AVX-512 fused-multiply-add instructions cost a lot more than 1 million loads (we can probably arrange for the right proportion of loads to hit a CPU cache vs. go to main memory, so that they end up taking the same time). Even without AVX, I imagine things lik…

oh that makes sense, i guess that would be another aspect to measure

Re: What should the CPU usage be of a fully-loaded CPU that has been throttled?

#179

Post by MauranKilom »

omegalulw wrote: post #177
MauranKilom wrote: post #149

Fun tangential anecdote regarding how interconnected and unintuitive CPU performance can be: I once made something run 20% faster by spawning a thread that did nothing but spin (i.e. while (true); ). I was trying to optimize some FEM code, toying with (hardcoded) solver parameters. On one console I had it spitting out the wall clock durations of time steps as the simulation was running, while on the other I was prepa…

I'm confused, how is COU speed tied to memory? AFAIK, memory is tied to CPU base speed which is almost always 100 MHz. The CPU then just scales it's own multiplier.

Northbridge frequency (as shown by CPU-Z) is correlated to CPU speed in my experiments. It's not one to one, but NB frequency definitely varies by a factor of two depending on CPU load.

What exact mechanism controls this is not clear to me (and I'm actually not sure if it's clear to anyone outside of Intel - the one paper [0] I found at the time was based on reverse engineering experiments). Nevertheless, CPU clock speed definitely affects Northbridge speed, as proven by the latter increasing from spinning a thread that never touches memory.

[0]: https://tu-dresden.de/zih/forschung/ressourcen/dateien/proje...

See section V.A:

> The results [...] indicate that uncore frequencies – in addition to EPB and stall cycles – depend on the core frequency of the fastest active core on the system.

(That conclusion is fully in line with my own observations.)

Also see the corresponding patent linked in the paper: https://patents.google.com/patent/WO2013137862A1/en

Re: What should the CPU usage be of a fully-loaded CPU that has been throttled?

#180

Post by nomel »

dataflow wrote: post #46
nomel wrote: post #43

Earlier quoted context omitted.

> If it's throttling to lower the temperature… This gives the ability to go over 100% before thermals equalize, since max power would follow a Newton cooling curve.

I don't follow. Whatever frequency the CPU is currently running at is a lower bound on the maximum frequency it could be running at, so it shouldn't exceed 100%?

But the thermals of the system means it can, for short periods of time, run much faster than long periods of time. I don't think a constantly changing 100%, that changes with temperature, is very useful. I would be more interested in whatever the sustainable 100% is, for normal room temperature.
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