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Performance "throttle back" problem.

10371 Views 16 Replies Latest reply: Mar 18, 2008 10:20 PM by Brian Caslis RSS
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Eric Beyer Level 2 Level 2 (285 points)
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Feb 19, 2008 6:19 AM
OK, so I know the MB Air isn't designed for this, but I've been playing World of Warcraft on it for a while. What I notice is that the performance is decent for about 10-15 minutes (~10-15 fps) but eventually degrades terribly (~3fps or less). During this time the fan is going nuts (~6200 RPM according to my status widget) and the back/left of the base gets hot.

I've read that the MB Air will shut down one core and throttle back the clock speed of the remaining core when it gets hot. Is this true? Can this be bypassed somehow? If so, is that a really bad idea? I'd prefer not to have to schlep a laptop cooler around if I don't have to.

Your thoughts, as always, are appreciated.
PowerMac G5 Dual 2 GHz, Mac OS X (10.5.2), Also MB Air 1.8GHz
  • Brian Caslis Level 3 Level 3 (795 points)
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    Feb 19, 2008 7:16 AM (in response to Eric Beyer)
    Yes, it's true if it gets really hot one core shuts off to reduce temperature. No, there is no way to override it. Yes, this is a bad idea. A slower computer is better than a melted one. The MBA is a good computer but gaming really isn't it's thing.
    MacBook Pro 2.4GHz 17" HD, Mac OS X (10.5), 4GB RAM, 200GB 7200rpm HD; iPhone
  • tele_player Level 5 Level 5 (5,380 points)
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    Feb 19, 2008 7:56 AM (in response to Brian Caslis)
    Agreed, but I'd use Activity Monitor to verify that it really is shutting down one CPU.
    MacBook 2.0GhzCore2Duo, 2.Gig, 160G HD, PowerBook G4 1.5Ghz 15", Mac OS X (10.5.1), Logic Pro 7.2.3, Focusrite Saffire...
  • mac wison Calculating status...
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    Feb 19, 2008 8:02 AM (in response to Eric Beyer)
    Do you really need to ask if this is a bad idea?

    Actually, this sheds some light on the limits of this notebook. From the looks of it,
    it's performance range is limited and fixed.

    which is understandable, as it's an unusual design.
  • Shaggywerewolf Calculating status...
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    Feb 19, 2008 9:35 AM (in response to Eric Beyer)
    Eric Beyer wrote:
    OK, so I know the MB Air isn't designed for this, but I've been playing World of Warcraft on it for a while. What I notice is that the performance is decent for about 10-15 minutes (~10-15 fps) but eventually degrades terribly (~3fps or less). During this time the fan is going nuts (~6200 RPM according to my status widget) and the back/left of the base gets hot.


    10-15 fps is "decent"? LOL...sorry, but I just couldn't help myself As everyone has pointed out already, this probably isn't the best notebook computer to be running games on.
    Mac Pro 2.66 2GB 2x500GB; 1.33Ghz 12" Powerbook 1.25GB;, Mac OS X (10.5), 1.5Ghz Core Solo Mini 2GB; 30GB 5G iPod (white); iPhone 8GB; APC RS1500
  • meyert Calculating status...
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    Feb 19, 2008 12:22 PM (in response to Eric Beyer)
    Good remark. So a far as i know and understand the OS is responsible for powering off the cpu core as ACPI can't do that. So what happens when i install windows or linux on a macbook air?
    Will the notebook still run stable under load? Or will ACPI power off the whole computer when reaching a critical temperature?
    Mac OS X (10.4.6)
  • ralphjjr Calculating status...
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    Feb 19, 2008 6:04 PM (in response to Eric Beyer)
    Eric,

    A few MBA users have been experiencing similar issues, not necessarily while playing World of Warcraft, but using other CPU and I/O intensive applications, check out this question: Kernel_task on a new MacBook Air


    Do you mind trying a few things? I think temperature is the answer. Can you measure the temperature? Also, what other processes do you notice taking up CPU time? Is kernel_tasks one of them?


    I think the problem is a combination of the temperature, perhaps a "busted" SMC and poor CPU management by the kernel. My friend has an MBA also and we have both experienced this issue in a variety of situations. I am almost 100% certain that the issue is temperature related, but is also caused by a buggy SMC. I think the SMC is having trouble with the temperature threshold and prematurely shuts off a core. I stress prematurely because I know CPUs should be able to handle temperatures in excess of 200 degrees Fahrenheit, approximately 100 degrees celsius. The application Temperature Monitor, tells me that the upper limit for each core is exactly 100 degrees celsius. In all my tests I have never passed 186 degrees fahrenheit, which is roughly 85 degrees celsius.


    Any additional readings, tests and experiments would be greatly appreciated.
    Macbook Air, Mac OS X (10.5.2)
  • Shaggywerewolf Level 4 Level 4 (1,495 points)
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    Feb 19, 2008 7:48 PM (in response to ralphjjr)
    True, while the specified upper limit (supposedly) is 100C, I'm willing to bet that Intel and/or Apple engineers never intended the CPU to actually sustain that temperature for any length of time. My guess would be that at such high temperatures, it may not be possible for the Air's cooling solution to deal with the heat, and the CPU may end up in a thermal runaway situation -- so the solution would be to prevent the CPU from ever getting that hot. It wouldn't surprise me if in addition to shutting down one of the cores, the remaining core is deeply throttled back in clock speed (to try and keep the heat dissapation to a manageable level), which could explain the significant performance issues as well.
    Mac Pro 2.66 2GB 2x500GB; 1.33Ghz 12" Powerbook 1.25GB;, Mac OS X (10.5), 1.5Ghz Core Solo Mini 2GB; 30GB 5G iPod (white); iPhone 8GB; APC RS1500
  • hsshoura Calculating status...
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    Feb 19, 2008 8:45 PM (in response to Shaggywerewolf)
    I can see how the throttling works - happens on my laptop when temps start to go over 72*C

    Get yourself a laptop fan stand for when you play WOW... it will keep the laptop cooler

    If you want a portable one get that thermal pad from Xioft and give it a try - it might help dissipate heat
    Custom Built, Windows Vista, Custom Built PC :)
  • zinch Calculating status...
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    Mar 12, 2008 5:07 AM (in response to hsshoura)
    I'm working on my MBA and it's happening right now; one of the CPU cores is off. The temperature is 65c and one of the cores has switched off. I'm certainly not doing anything particularly taxing, there's really no excuse for this. Has Apple acknowledged this as being a problem yet?
    MacBook Air, Mac OS X (10.5.2), None
  • permamac Calculating status...
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    Mar 13, 2008 1:04 AM (in response to zinch)
    I'm on my third Air, and this one works wonderfully. I was so incredibly frustrated with the core shut-downs and overheating. i've been pushing this new air to the limit with simultaneous streaming video, and multiple adobe apps running, and it never overheats, and the core never shuts down. It has to be an issue with thermal grease application, or other defect, because it is a night-and-day difference. third air was the charm.

    I couldn't even connect an external monitor without my last air shutting down a core after a few minutes. Now I can run all day long without a wimper.

    If your Air is doing this, take it back to Apple. I almost gave up on the Air, but I'm super-glad that I didn't. I love it now.
    Macbook Air 1.6, Mac OS X (10.5.2)
  • zinch Level 1 Level 1 (0 points)
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    Mar 18, 2008 4:23 AM (in response to permamac)
    Thanks, I'm going to do this. Did they replace it for you there and then? This is my only computer and I use it for work daily; I really hope I don't have to go through 3 of them to get a working one!
    MacBook Air, Mac OS X (10.5.2), None
  • Armand Loonux Calculating status...
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    Mar 18, 2008 4:59 PM (in response to hsshoura)
    what laptop do you have? MBA?

    I have been playing Unreal Tournament 2004 on my Penryn 2.4 GHZ MBP with all settings turned to HIGH (even the in-game announcer bot exclaimed, "Holy ****" when I was turning up the game's video/graphics settings. People familiar with UT2004 should know what I'm talking about) for the past one and half hour. The performance was awesome. No lag, frame drops, symptom of CPU core shut-down etc. So I suddenly quit the game and instantly looked at istat's readings. fan speed was something like 3500 for both fans but the temperature was an alarming 167 F.

    Is this normal?

    Sorry for irrelevancy, but I believe you have more experience than me when it comes to gaming and heat on modern notebooks. So please shed some light on it. Thanks
    MBP Penryn 2.4 GHZ Matte Core 2 Duo, 2 GB RAM, 200 GB HDD, 8600 GT 256 MB GDDR3, Mac OS X (10.5.2), 8 GB Iphone
  • Brian Caslis Level 3 Level 3 (795 points)
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    Mar 18, 2008 5:35 PM (in response to Armand Loonux)
    Sounds completely normal. I've been trying a penryn 2.6GHz MBP and the heat improvement is impressive (compared to previous MBPs). Nothing I've done has been able to get the fans higher than 3500rpm, most of the time they are 2000rpm even when encoding a video. I assume your temp is the CPU? If so, that sounds pretty normal also.
    MBP 15" 2.6GHz 4GB, 200GB HD, Mac OS X (10.5.2), MBA 1.8 64GB SSD; iPhone
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