Underclock the 4Ghz i7?

Discussion in 'iMac' started by rainydays, Nov 6, 2014.

  1. rainydays macrumors 6502a

    Nov 6, 2006
    I'd really love to have the hyper threading in the i7 but it just puts out too much heat. I'd happily pay the same price for a 3.4GHz i7 instead.

    Is it possible to underclock the 4GHz i7 in a reliable way? As I understand it this processor is unlocked. But how would I go about it? I've never been into the overclocking scene so I'm a total newbie.
  2. Pressure macrumors 68040


    May 30, 2006
    What do you mean by "puts out too much heat"?
  3. rainydays thread starter macrumors 6502a

    Nov 6, 2006
    It's running hot, making the fan ramp up way to quickly. I don't mind running at a lower clock speed. The performance gain by going from i5 to i7 at the same clock speed is quite substantial in apps like Logic.
  4. ikaka macrumors regular


    Mar 5, 2009
    It will just run hot if used. Nothing will happen to the iMac.
  5. rainydays thread starter macrumors 6502a

    Nov 6, 2006
    I know. But excessive fan noise is a deal breaker to me. Still I would like an i7 CPU. The 2013 3.4GHz i7 model is not that touchy. That's why I'm asking if it's possible to downclock it.
  6. xgman macrumors 601


    Aug 6, 2007
  7. boast macrumors 65816


    Nov 12, 2007
    Phoenix, USA
    You can manually set the CPU fan, and rely on the CPU throttling down due to heat.
  8. 932393 macrumors newbie

    Nov 7, 2014
    at what temperature does throttling happen please?
  9. FroggyTaco macrumors newbie

    Feb 25, 2015
  10. Melodeath macrumors 6502a

    Dec 9, 2009
    Is the fan really ramping up during Logic use?
  11. bladerunner2000 macrumors 68020


    Jun 12, 2015
    It's actually already throttled, LOL! Go to the 2:30 minute mark and watch Linus explain the performance.

    Here's the thing; you'd think that with such bad cooling in the iMac Apple would have gone with a lower clocked CPU, but they can't because Intel has nothing else. You also gotta wonder why they even bothered to use the 4790k if you can't overclock it. Well, that's likely because the 4790 (non-k) CAN'T be underclocked!

    So because Apple is dumb enough to put more emphasis on form than function, this forces them to go with a more expensive processor, downlock it, and add poor cooling/airflow to it AND charge a premium price for it.

    So, while you are technically getting a 4790k processor, you are NOT getting its advertised performance..... ou, I smell class action lawsuit.
  12. Significant1 macrumors 6502

    Dec 20, 2014
  13. gnasher729 macrumors P6


    Nov 25, 2005
    When it gets too hot. CPU throttling due to high temperature is the last resort to prevent damage if the fans are broken. You should absolutely not play with the fans and rely on CPU throttling, and CPU throttling should never happen. Imagine your car has its engine limited to 6000 rpm to prevent engine damage. Going in first gear at 6,000 rpm is still a very, very bad idea and will destroy your engine sooner or later.
  14. JoelTheSuperior macrumors 6502


    Feb 10, 2014
    London, UK
    Right I love a bit of Apple bashing but what you've written simply isn't true.

    First of all, Apple haven't underclocked the chip at all. The Intel chip itself will underclock when the temps get too high automatically - as far as I know this is functionality of the CPU / the chipset itself and not anything Apple has changed. This functionality exists in all Intel CPUs - not just the K series ones. If it didn't you'd get a load of dead laptops with non-K CPUs because their cooling isn't up to the task.

    There isn't a class action lawsuit because the chip can run at 4Ghz just fine - just if it's doing anything intensive at that clock speed it'll get too hot and it won't be able to run at its full performance because it'll underclock to keep the temperatures within tolerable ranges.
  15. MacUser2525 macrumors 68000


    Mar 17, 2007
    Well that is quite the leap of logic for someone who lives in a country with the The Sale of Goods Act which says "goods must be as described, satisfactory quality and fit for purpose. If goods are faulty, you can claim from the retailer." Just in case you do not know your own laws I would say a computer that will not run a processor at full load for any length of time, which is mostly the entire purpose of getting a fast processor, is not fit for purpose.
  16. jerwin macrumors 68000

    Jun 13, 2015
    Intel Ark for the 4790 and 4790k
    The non-K version is 3.6, with turboboosting up to 4.0 Ghz. The K version is 4.0 Ghz with turboboosting up to 4.4 Ghz.

    Intel says that the 4790k can be turboboosted up to 4.2 Ghz with all for cores active.
    The 4790 likewise can be boosted to 3.8 Ghz with all four cores active. So by speccing a 4790k, Apple gets 200 Mhz over the slower chip

    So I suppose this all depends on whether you think turboboosting all the time should, or shouldn't be the default condition.

    Here's how the 4770k behaves in an imac

    3.9 Ghz to 4.0 Ghz with all four cores active. Still 100-200 MHz over the turboboosted 4770.

    Does anybody else find Linus Sebastian to be somewhat annoying?

    Anyway, I have the i5, so I don't really have a dog in this fight.
  17. aliensporebomb macrumors 68000


    Jun 19, 2005
    Minneapolis, MN, USA, Urth
    Rainydays - are you running iStat menus? I'm doing an informal survey on this. I am, for the record.

    Are you utilizing a lot of mics in your setup? I'm only a little concerned because the vocal booth we built to the back of our studio space is about 7 feet from my mac.

    But I've got curtains over entrance to the booth and the voiceovers my wife does are typically recorded to her own 2009 i7 mac. In those cases I'll have mine idling but my own projects tend to be very layered soundtrack type productions.

    Linus is annoying at times but he's not completely incorrect. But he's not spot on either.

    Still: I wrote this last night on 4790x temperatures, how that data is acquired in the chip and how some of
    the data is approximated (so not completely accurate) and some are from sensors and some processes that hit the FPU harder cause the chio to heat up hot by design so using other processes keep the chip cool.


    In brief: there are sensors for some of the temperatures but not all of them.
    Some types of mathematical processes in the chip make it raise in temperature more than others specifically AVX code that used to be running on the main CPU is now being run on the math coprocessor which produces what one individual said were unrealistically high temperatures.

    I'd be curious if Logic is running its code on the math coprocessor or the main cpu.

    I'm running logic over here and have a rather large session. I'm going to see (once it copies from a backup drive) what it does to the fan SPLs using a decibel meter I have.

    Stay tuned...
  18. aliensporebomb macrumors 68000


    Jun 19, 2005
    Minneapolis, MN, USA, Urth

    Was running some "19 layer wedding cake music".

    One was 82 tracks of which 24 tracks were for drums alone. Another was 53 tracks and a couple of subs. I used the fan control in iStat Menus and it kept the fans quiet even when pounding 82 tracks and a few subs. It kept the temps just below 60c and everything seemed frosty.

    My experience - even running massive amounts of tracks the cpu has plenty of headroom to run these sessions without ramping up the temps hugely. Even with the fans on quiet setting.

    Mind you, I'm in an air conditioned place and a somewhat dark room and your mileage may vary if you run with no aircon. I also have fans for running between takes if it gets too hot in here.

    Give it a shot.
  19. dyn macrumors 68030

    Aug 8, 2009
    From ark.intel.com:
    Both the 4790 and 4790K support that feature so both are able to underclock themselves due to thermals.

    Apple hasn't underclocked any Intel CPU and never overclocked one either until the Core M in the MacBook (and iirc this chip is designed for that; I think it is called "Configurable TDP-up"). Apple runs these chips at the default specs (probably due to them being the most optimal).

    Another thing to note: just because a machine gets noisy doesn't mean it has bad cooling, it's just noisy. Could be the fans they use. Iif you look at the tear down you can see the fan is not a very big one which usually means that it'll be noisy. Had they used a bigger one the noise problem with be far less.
    If the cooling isn't adequate and the cpu continuously throttles back then you can say the cooling is bad. However, I haven't seen any proof of throttling;the graphs and images I've seen only show the cpu is scaling up and down with its frequency quite rapidly (which is its normal behaviour) whereas with throttling you'd see the speed go down gradually (it becomes slower and slower thus the max frequency gets lower and lower).

    The cpu isn't the only component getting hot. The gpu gets much hotter much quicker. In my case I'm seeing 10 to 15C difference between cpu and gpu temps (with the gpu being the highest). The temps are not different from what I'm used with notebooks with a dgpu (Nvidia, AMD/ATI).
  20. jerwin macrumors 68000

    Jun 13, 2015
    I suppose that the proper benchmark would be to take several computers of different configurations, run the same demanding (and time consuming, as heat does take a while to build up) workload on each of them, and measure fan noise.

    Not "fan speed". Not "cpu temperature". But actual noise produced by each computer.

    It may be that the i5/m290 is better than any i7 for your purposes. It may be that the mac pro is the only apple computer that's fast enough to handle your workload and still remain relatively silent.
  21. aliensporebomb macrumors 68000


    Jun 19, 2005
    Minneapolis, MN, USA, Urth
    My point is: I'm running more tracks than most sane people and I never once went into high temps with loud fans. What kind of session is the OP running?

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