I'm a heavy number cruncher. Should I even consider the Air?

Discussion in 'MacBook Air' started by Adam Ierymenko, Mar 7, 2008.

  1. Adam Ierymenko macrumors newbie

    Mar 7, 2008
    I do a lot of heavy number-crunching stuff like evolutionary computation, N-body problems, etc.

    I'm aware that the Air is a bit slower than the other laptops, but this isn't a show-stopper as I have another bigger desktop beast to run things on when I really really care. I also know that doing this while on battery won't get you very far, but that's true of any laptop. I only run such things for any length of time with the power connected.

    But the thing that's giving me pause is the reports of heat problems and cores shutting down with heavy CPU use. Could the Air even handle something like running genetic programming for 8 hours?

    For instance, what if I were to max out both cores for 12 hours with the power connected and in a normal temperature room? Would it melt into a puddle of molten aluminum and chip parts, or would it actually handle it without core shutdowns or other nastiness? Obviously the fan would whirr and it would get hot, but that's to be expected. But would it survive to complete the job, or would it collapse into a pathetic pile of single-core overheatedness?

    Could some brave souls out there with the Air actually do this and report the results? Run two concurrent movie encoders for a long time or some other CPU-bashing task and see what happens? I'm sure lots of readers would love to know.
  2. mashoutposse macrumors 6502

    Dec 13, 2003
    The MBA does not like CPU-intensive tasks. The power is more than adequate... until the heat becomes overwhelming and the second core shuts down.

    However, it should be fine if you use it on a table and ensure proper ventilation.
  3. macanudo macrumors regular


    May 9, 2006
    Philadelphia, PA
    1.6 and 1.8GHz dual processors are good enough, but the MBA wasn't designed for CPU intensive tasks. I'd consider the MBP instead.
  4. al82 macrumors regular

    Feb 13, 2008
    "Run two concurrent movie encoders for a long time or some other CPU-bashing task and see what happens?"

    not sure what this but if i watch a avi file for more than 20 mins the thing slows down and makes watching movies or even you tube videos impossible.
  5. Eraserhead macrumors G4


    Nov 3, 2005
    The high end MB is still fairly portable and is almost as powerful as the MBP, especially in the processor. So I'd recommend that.
  6. Sage Harupyuia macrumors member

    Mar 8, 2008
    The MBA is meant more for stealing the show during presentations and 'showing off'. ;)

    You would be better off running your work on a Macbook or a Macbook Pro.
  7. Father Jack macrumors 68020

    Father Jack

    Jan 1, 2007
  8. Adam Ierymenko thread starter macrumors newbie

    Mar 7, 2008
    Tried it in store, will try again before buying

    I tried this in the store:


    Max'ed out both cores for about 20 minutes. It got a little warm, but that's about it. Results seemed quite different from the extreme heat and core shutdowns reported here.

    Could some of you download that and give it a shot? Set it to run two instances for an unlimited amount of time and let it run.

    I'll try it again before buying. I might ask them if I can take my actual unit that I purchase for a test-drive in the store and load the hell out of it-- run CPUTest on both cores while watching full-screen video or something like that. If it buckles, I'll get a different laptop line. I'll report the results here.

    I've seen the rumor multiple places that early MBA runs had heat problems and that this was a manufacturing issue. I'd really advise those of you having these issues to go into a store and try the same test with the demo unit sitting there. If it doesn't do the same thing, your unit probably needs repair. This should be covered by the warranty since, at least as far as I'm concerned, I expect any computer system to be able to achieve its advertised computational throughput under normal ambient heat and ventilation conditions.

    Maybe they did something dumb internally like this:


    Heh... or forgot the heat compound in their first run. A Core 2 with no heatsink compound will go critical like Chernobyl.
  9. Phil A. Moderator

    Phil A.

    Staff Member

    Apr 2, 2006
    Shropshire, UK
    Doing it now - will let you know how it gets on in an hour's time
  10. Adam Ierymenko thread starter macrumors newbie

    Mar 7, 2008
    Great. I really think it's important to test this with a basic CPU burn-in app instead of with YouTube so as to rule out bugs with Flash, Safari, etc. Flash can be a piece of you-know-what and I've seen it have problems, crashes, stutters, etc. on all kinds of machines and OSes.

    Could you, while bashing your CPU, also run something that give you some idea of its performance? I'm curious about whether it shuts down cores or clocks down.

    Another note for readers: the "core shutdown" reported by YouTube viewers might not be a core shutdown at all. If you're seeing one core go flat in the monitor, it might just mean that some app has decided to stop being multi-threaded. Maybe Flash has a thread deadlock bug, which would cause something that would *look* like a core shutdown in a CPU meter. OSes typically have a concept of "CPU affinity" where they assign apps to primarily use one core over another for better cache efficiency. Seeing one core max'ed out and the other dead would be normal for a heavy CPU use single-threaded app.

    Another point for the YouTube complainers: my 900mhz G3 iBook can watch full-screen video. So video stuttering should not occur even if one core of a Core 2 Duo is shutting down or even if the CPU is clocking down. That *really* sounds like a software issue with Flash or Safari/Firefox.
  11. Techguy172 macrumors 68000

    Feb 2, 2007
    Ontario Canada
    I still think you would be better off with the Macbook or Macbook Pro just because when that computer gets hot it's done it just slows down and dies.
  12. mctheriot macrumors regular


    Nov 2, 2007
    McHenry, IL
    Monitor Both Cores

    Where are you able to see both cores? The only thing I see is temp of core A in iStat.

  13. Phil A. Moderator

    Phil A.

    Staff Member

    Apr 2, 2006
    Shropshire, UK
    OK, one hour later and here are my observations (1.8 SSD):
    1) CPU utilisation was pretty much 100% solid across both cores for the whole hour
    2) No core shut-downs
    3) CPU Temperature was kept below 70 degrees by fan (Which went up to 6,200 RPM)
    4) Things slowed down as you would expect when both cores are being hammered, but not dramatically enough to suggest a clock speed reduction. I did some heavy compilations in Visual Studio in a Win2K3 VM and it still kept working OK
    5) As soon as I stopped the CPU test, the temperature started dropping and the fan started slowing down

    iStat readings at the end of the test (temps in celsius):

    Fan: 6200rpm
    CPU A: 68
    Heatsink A: 56
    Enclosure Bottom: 44
    Airport Card: 40
    Power Supply 1: 61
    HDD: 0 (always reads this, could be because I'm SSD)

    iStat readings 10 minutes after the end of the test (temps in celsius):

    Fan: 2900
    CPU A: 52
    Heatsink A: 52
    Enclosure Bottom: 41
    Airport Card: 36
    Power Supply 1: 54
    HDD: 0

    In short, the MBA behaved exactly as any other notebook would: Give it some heavy work to do and things will heat up leading to an increase in fan speed to cool things down. The fan keeps things under control and then when the heavy load is removed, the fan cools it back down and the speed of the fan then drops back down again.

    If people are seeing core shutdowns, etc, then I would say there's a problem with their machine and they should get it sorted out.
  14. Adam Ierymenko thread starter macrumors newbie

    Mar 7, 2008
    I agree.

    I'll stress-test mine in-store, but it sounds like there might be some MBAs out there with manufacturing defects. Such things are common in first runs. Your behavior sounds like what I experienced with my older generation Macbook Pro and with my old Panasonic Toughbook.

    People could also be mistaking a bug in Flash for a hardware defect.
  15. Scott6666 macrumors 65816


    Feb 2, 2008

    No. Waste of time. Don't try until the kinks get worked out.
  16. Adam Ierymenko thread starter macrumors newbie

    Mar 7, 2008
    Heavy number cruncher reviews the Air

    Well I've had my Air for several days and would like to post a review. In short, I love it, but there are a few rough spots.


    First, the heat issue:

    I have some answers that I haven't seen mentioned yet, so read this!

    It isn't a problem for me even when max'ing out both cores heavily unless an external monitor is plugged in!!! If an external monitor is plugged in, the fan runs at 6200RPM constantly even when not max'ing out the CPU. When the CPU is max'ed and an external monitor is plugged in, I get the emergency core shutdown thing after blasting both cores for 10-15 minutes or so.

    So the Air does appear to be able to dissipate the heat of either the CPU or the GPU fully cranked but not both at the same time.

    The really makes a fair amount of sense. A video chip is basically another CPU, and driving a DVI monitor means that this other CPU has to push a massive amount (about 3-8gbps) of data constantly out through the DVI port while at the same time rendering all OSX's eye candy and driving the regular built-in monitor. Plugging in an external monitor more than doubles the GPU's workload.

    But without an external monitor I can max out both cores of the main CPU without any serious heat problems as long as the external vent is un-obstructed. I ran a test for hours doing fourier transforms an all sorts of heavy stuff and it was fine. Fan goes to 6200RPM which is to be expected when beating up a laptop, but no down-shifts or core shutdowns. Temp stays around 80C (CPU) and 58C (heatsink) on mine.

    Obviously the external power is connected; max'ing out any laptop CPU on battery will drink up your milkshake pretty fast.

    I bet you could get it to handle both the CPU and GPU running full blast if you built some kind of custom desk-rest that actively cooled the bottom of the aluminum case. Aftermarket item? :)

    I also noticed that if I set the Air on top of a book that's smaller than the Air's footprint with its butt hanging off the back (rear of bottom case and vent exposed to air) this helps control the heat a bit. When I do use it with an external monitor I set it on my desk like this. A little stand that left the whole bottom exposed would probably work even better. But most of the time I don't use the Air with an external monitor, so this really isn't an issue for me very often.

    If you are having severe heat problems (more severe than I describe) then you almost certainly have a defective unit. When I bought the Air the salesman said that if I had severe heat problems this would be covered by the warranty and I could bring the unit back for another one. He mentioned that some early run Air units might have had bad thermal paste jobs, so here we have another confirmation that this issue exists and is out there.


    Other stuff:

    Build quality is excellent. Screen is very good, and the brightness range is amazing! It goes from very very dim to almost ridiculously bright. I can use it in direct sunlight. The case is perfectly assembled, keyboard feels great, etc.

    I only noticed two nit-picky quality issues.

    1) With the brightness all the way up I can see some very minor "grain" in the background of the display and the bottom right corner is just slightly dim vs. the rest of the display. You have to load a solid grey background and look really closely to see this, and you can't tell at all during normal operation or with the brightness not near maximum. This doesn't bother me at all.

    2) The Airport antenna is just slightly off center and about 1mm shorter than the space it fits into. I'm not OCD enough to care about this. I didn't even notice until I read someone else's review and they reported this on theirs.

    Performance is very good. Subjectively it feels as fast as my old 2.0ghz Macbook, and memory bus performance is actually better. The heavy crunching stuff I do tends to be memory bound, so the Air actually performs surprisingly well. Video performance feels identical to the Macbook, which makes sense since it's the same video chip. Haven't noticed the hard drive being too slow, but it is slower than the Pro. (I have the HDD model.)

    Loudness, or lack thereof: hard drive is inaudible, and the fan just barely whirrs even when at 6200RPM. When at 2500RPM (the usual speed) you have to hold it up to your ear to hear it.

    Battery life: I find that I get from 3.5 hours (doing a bit heavier stuff) to 4.5 hours (typing, checking e-mail, etc.) battery life. I've only run it down twice though to calibrate it, and I didn't time it rigorously. So those are subjective anecdotal numbers. But the battery life feels fine. Not excellent and not five hours, but fine for my needs.

    Lack of ports isn't an issue at all for me. If you need lots of ports, the Air isn't for you.

    Summary: fantastic, sexy, beautiful ultraportable laptop that's a pleasure to use and that packs enough power for even demanding tasks like genetic programming, rendering, scientific computing, large software builds, etc. as long as you give its fan some breathing room. (Give it some air... wah wah wah... :)

    Wish list: address the video chip heat issue, 4gb RAM, larger HDD or cheaper SSD.
  17. MacFanBoyIIe macrumors 6502

    Feb 22, 2008
    No, the MBA isn't designed for that.

    If you need portable number crunching power, buy a Mac Pro and a VERY big backpack. :D
  18. Adam Ierymenko thread starter macrumors newbie

    Mar 7, 2008
    It's not designed for it, but it can do it... when plugged into external power of course. :)

    I think my finding about the external monitor heating the unit up is important. I wonder how many people having heat problems have external monitors plugged in? Try doing CPU burn-in on your unit without one and see what happens.

    There is a bit of a nasty side effect to this though that I forgot to mention: you can't really watch full-screen flash videos with an external monitor plugged in without possibly running into heat issues. That's in some ways Adobe's fault-- Quicktime and MPlayer can play movies without beating up the CPU anywhere near as much as Flash. Flash performance on OSX really sucks. Complain to Adobe.
  19. jiyang71 macrumors newbie

    Jul 5, 2007
    Thanks for sharing great finding.
    Do you think it will hold still with bootcamped XP? Have anyone tried this?
  20. bluebomberman macrumors 6502a


    Jan 9, 2005
    Queens, NYC
    A little late for your not-so-useful advice, considering the original poster posted that he/she bought the Air before your post. :mad:
  21. MacFanBoyIIe macrumors 6502

    Feb 22, 2008
    Don't be so dense, it's not becoming. :D
  22. abijnk macrumors 68040


    Oct 15, 2007
    Los Angeles, CA
    Might I ask what in the world you are talking about? I didn't know you could see the airport antenna from the outside... :eek:
  23. izibo macrumors 6502

    Oct 6, 2004
    Having had a Week 2 unit and a brand spanking new unit, I can say that the core shutting down problems have been resolved (at least under my conditions). Safe to say that a new unit would be problem free!
  24. bcaslis macrumors 68020

    Mar 11, 2008
    I ran this on my week 3 MBA 1.8 SSD for an hour. Highest temp I saw was CPU of 82C, most of the time it was about 80C. Case was slightly warm on the bottom back. No core shutdowns or problems, fans were at 6200 rpm most of the time but slowed after a couple of minutes.

    I also ran it on a new MBP 2.6GHz. Highest CPU I saw was 67C. The dual fans stayed at their default of 2000 rpm and never went up. Case temperature about the same as on the MBA.

    I firmly believe there isn't any general heat problem on the MBA but can be broken down into 3 categories:

    1.) Defective machines. It happens, get them replaced or repaired.
    2.) People running it on a soft surface. The vents in the back are almost immediately blocked on any soft surface unlike the MB or MBP. This will block ventilation and eventually cause overheating. Don't do this if you are running CPU intensive stuff.
    3.) Flash movies/videos. This is using both the GPU and the CPU and will generate the most heat. It's long been shown that Adobe's implementation on the Mac is worse than on Windows and this is clearly evident on the MBA. I've played full length quicktimes without problems. The fans do come on and the case back bottom gets warm, but it works OK. Any flash youtube video cause the fans to come on sooner and faster than other formats. I haven't run anything there for hours so I don't know if it will eventually shut down, but I haven't seen any stuttering or core shutdowns in ones that ran for 5 minutes or so.
  25. Adam Ierymenko thread starter macrumors newbie

    Mar 7, 2008
    That's almost identical to my results w/o an external monitor.

    Did you have an external monitor plugged in?

Share This Page