15 W TDP Notebooks: Is the fan always shut off during low performance use?

[Fjodor2001]

Hi,

I just wonder under what conditions the fan normally turns on for Notebooks/Ultraboks using Intel 15 W TDP CPUs? E.g. for units using Intel i5-4200U, i5-4500U, i5-4550U, i5-5200U, i5-5500U, i5-5550U and similar.

1. If you're only surfing the web, reading email, or viewing some document, is the fan shut off all the time? Or does it periodically turn itself on for some time, and then shut off again?

2. How high does the workload have to be for the fan to turn on, at least periodically? E.g. does that happen when gaming, when viewing 1080p movies, or similar?

3. Is there any way to easily configure the unit to a "low power" mode, so that it preferably runs slower, rather than turning on the fan at any time?

The reason I wonder is that I'd like to have a Notebook/Ultrabook that is completely silent most of the time. However occasionally when higher performance is needed (e.g. when compiling source code or doing video conversion), it's ok for the fan to turn on.

Any experiences are appreciated!

 

[dave_the_nerd]

Generally the fan is shut off at near-idle use (web surfing, word processing) even on fairly high-powered laptops.

But it depends on the laptop design more than the CPU.

 

[ninaholic37]

But it depends on the laptop design more than the CPU.

I've noticed this too. The laptop manufacturer's default settings are not always similar, even when the exact same CPU is used.

On my Thinkpad T42, the fan will turn on loudly at about 48 degrees (regardless of what state the CPU is in), which is pretty low/conservative... I think it's because they want a "cool palm rest/trackpad" and to prolong it's death. On my Latitudes, each one is different, the older Dothans seem to only come on when the CPU is not idle (600mhz) but the newer Dothans seem to come on even when it's in idle sometimes (800mhz)... I'm not sure if it's time or temperature based. On my Asus (also Dothan), the fan RPM will crank up at 57 degrees... which is high enough that if I run the CPU at 600mhz always, I'll pretty much never hear it.

 

[IntelUser2000]

The reason I wonder is that I'd like to have a Notebook/Ultrabook that is completely silent most of the time. However occasionally when higher performance is needed (e.g. when compiling source code or doing video conversion), it's ok for the fan to turn on.

Any experiences are appreciated!

You can just turn on Power Saver mode. That's probably the best way to lock it at LFM frequency. On my 17W Ivy Bridge Ultrabook, #1 is true, #2 can happen sometimes on picture-heavy sites like Engadget scrolling, definitely on Youtube.

On my device fan engages when viewing Youtube 1080p even on Power Saver mode. Hopefully 15W Haswell helps.

The fact is while they trump GPU offloading to save significant power on video viewing, unless you have it downloaded you aren't guaranteed to get that support. On most online viewing it'll probably rely mostly on GPU.

 

[Lonyo]

You can usually set up the power profiles on most laptops to do this.
Set a power saver with max frequency locked to something like 50% and passive selected as the cooling option, and then a normal profile where the CPU can go to 100% (and you can still set it as passive cooling).

I do this with my tablet and it means if I'm doing light stuff it's cool and silent, but if I'm doing something heavier I can switch to the higher power profile and it will get hot and noisy but have more performance (obviously).

Control Panel -> Power Options -> "Change Plan Settings" -> "Change advanced power settings".
Then you just fiddle with "Processor power management".
I have one profile which is set to Passive system cooling policy and 50% max processor state, and one set to passive and 100% max processor state.

If you also select to always show the battery icon in the taskbar you can quick switch between the two power profiles.

 

[Zodiark1593]

On my laptop, there is a BIOS setting that allows the fan to go off when temps allow. Issue is when it spins back up, it goes to full speed then back down. Currently, the fan never switches off in Power Saver, but it is barely audible even in a silent room, and the laptop will clock down the CPU (sometimes as low as 200 MHz) before ever ramping up the fan. On high power mode, it's a different story. Note: It's an i5 460m.

 

[sm625]

Careful when comparing youtube performance. The windows 8 youtube app uses less cpu compared to youtube in a browser, so there is a better chance it may handle that without revving up the fan.

 

[Fjodor2001]

You can just turn on Power Saver mode. That's probably the best way to lock it at LFM frequency. On my 17W Ivy Bridge Ultrabook, #1 is true, #2 can happen sometimes on picture-heavy sites like Engadget scrolling, definitely on Youtube.

On my device fan engages when viewing Youtube 1080p even on Power Saver mode. Hopefully 15W Haswell helps.

On the laptop I have at work (35 W TDP, and probably SB based), the Power Saver mode does not guarantee that the fan never spins up. It just prioritizes lower frequency over max performance, which results in less fan usage.

So is there any mode on 15 W laptops that guarantee that the fan will never spin up? Basically it should lower the CPU frequency to such a degree that fan usage is never needed.

 

[ninaholic37]

So is there any mode on 15 W laptops that guarantee that the fan will never spin up? Basically it should lower the CPU frequency to such a degree that fan usage is never needed.

I think you would need to go further and find a Fan Control program for your laptop (or create one if it doesn't exist yet). I know there is one for my Thinkpad that people have had a lot of success with (apparently if you set the high RPM modes to 55 degrees, you should almost never hear it as the temperature usually doesn't go that high anyway). This may have a slight impact on how long the laptop lasts, but most people who tweak their fans don't seem to care... if you buy a new one every 2 or 3 years I don't think it's worth hearing the noise.

I remember hearing that lots of the first light Ultrabooks ran hot and had annoying fans, but you would think this would be improved over the years from experience and with Broadwell though (maybe not because it's still the same TDP?). My old Pentium 4-M had an annoying fan too, I think it was 35W, I let my dad have that one though and he gave it to a friend so I didn't have much of a change to play around with that beast.

 

[Fjodor2001]

There really should be some explicit common test metric for this. Something like this:

"To what frequency can the CPU be clocked continuously while guaranteeing that the fan will never turn on at 25 degrees C ambient?"

 

[Fjodor2001]

Just thinking: Let's assume laptops had an option to "never turn on the fan, instead lower performance" option. Then wouldn't the Intel Broadwell Y Core M CPUs at 4.5 W TDP be pointless?

As I understand it, their main purpose of that CPU model is to enable fanless laptops. But you could just as well use an Intel Broadwell 15 W TDP CPU, and set the option I just mentioned. And then on occasions when higher performance is needed you just set the laptop to high performance mode. Seems like that would be the best solution, since you get the fanless option while still allowing for higher performance on demand?

 

[ninaholic37]

I dug up some of the TDP datasheets from Intel.com because I was curious too :awe:

Haswell-U:

Broadwell-U:

Pentium M Dothan:

The old Pentium M Dothan looks like it has a lot more flexible speedstep to me:

7.5W TDP (600 MHz) to 21W TDP (1.5-2.1 GHz). Gen 1
10.8W TDP (800MHz) to 27W TDP (1.6-2.26GHz). Gen 2
3W TDP (600MHz) to 5.5W TDP (1.0-1.3GHz). ULV

This is probably because the Pentium M TDP didn't "cheat", it advertises the high TDP as normal, whereas Haswell and Broadwell use a "base" TDP (15W) as normal, and "turbo" TDP as even higher (25W). Broadwell even goes further and doesn't list what it's "turbo" TDP is at all, only saying that it's base is 15W TDP, and doesn't even say what the LPM TDP each model is either. All it has is a disclaimer:

"13 - LPM power level is an opportunistic power and is not a guarateed value as usages and implementations may vary." (5th generation Intel® Core™ processor family Datasheet volume 1, page 63)

Considering that Core-M (4.5W) uses 3.5W TDP at 600MHz, and Broadwell-U (15W) uses 9.5W TDP at 600MHz, my guess is that Broadwell-U won't be able to use 4.5W TDP at it's lowest frequencies @ 500MHz CPU / 300MHz iGPU. But I don't know, someone who understands the inner workings of these new CPUs or who already has one of these 15W chips might be able to give more exact details. :biggrin: