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Performance "throttle back" problem.

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

Posted on Feb 19, 2008 6:19 AM

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16 replies

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.

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.

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.

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.

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

Mar 18, 2008 7:32 PM in response to Brian Caslis

Hey Brian, thanks so much for such a prompt reply and sharing your observation. I'm at Starbucks right now and can't fire up the game and copy and paste all temperature readings from istat (didn't bring the mouse). But as soon as I reach home, I'm going to do it and let you and everyone else know. you're right. There's been a huge heat improvement. I barely heard the fan noise while playing UT2004, while on the two-month old MBP, the sound could wake up my next door neighbor. I know I'm exaggerating a little, but the previous one was seriously hot and louder even when the game was running with most of the graphics settings set to medium, while i barely hear the fans even with all settings set to high.

Performance "throttle back" problem.

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