Core shutdown--a dissenting opinion

[DJGuy]

First let me say that the dissenting opinion does not originate from me. A company IT guy was installing some software on my MBA, and noticed I had Activity Monitor running. He advised me that this will slow the machine a little. I replied that I'd had a core shutdown and so I was keeping my eye on the cores. "What?" said he. He then proceeded to tell me that a core shutdown is normal. Well, having read a lot of posts here, and posting some myself, I figured he might be nuts, or incredibly ill-informed. But he was quite insistent, and he was definitely a Mac guy, not a Windows guy.

At any rate, I kept Activity Monitor on the rest of the day. Some things I observed:
*If you display just the bars, and not the running chart, sometimes a bar will transiently go to zero, but then come back on seconds later. I wouldn't consider this to be a real core shutdown, but it could look that way.
*Some normal processes do seem to have a normal core shutdown. I found that if I turned on my screensaver (just one of the regular Apple options) for a minute or so, then turn it off, the Activity Monitor shows that only one core had been running while the screensaver was on.
*Usually I associate a core shutdown with extremely slow response, jumpy mouse, etc. But there was a time today, just some random configuration of maybe email and Word or something, when a core shutdown. But the mouse response was fine and if Activity Monitor wasn't running, I might not have know a core was out.

Nevertheless, I can still find extremely slow response at the same time as a core shutdown. Though now I think there are other factors involved.

 

[dudup]

Please notice that there are some apps which doesn't benefit from multiple cores -- the Adobe Installers are the most (in)famous examples. So it is normal to have just one core working.

You can be sure that you're having a core shutdown when your mouse cursor becomes laggy.

 

[wolfman28]

Hi there

I've been following the posts about the MBA for a couple of weeks since I am considering buying one.

When I read about the core shut downs I was at first very disappointed but the I started to monitor my Sony Vaio SZ closely and realized that it also gets very hot from time to time and the core shut downs happen which last for a couple of seconds.

My conclusion is that qite a lot of notebooks get hot and that core shut downs can happen regardless if it is an Apple or some Windows machine.

 

[Macmel]

I am using a MBP and I normally watch movies and youtube videos for more than one hour. Never got something nearly similar to what you describe. It gets hot, yes, but fans only rarely go over 2000 rpms and of course it never slows down.
That's what you get with your ultraportable...

 

[Alan Taylor]

I think a lot of people are mistaking single-core apps as a core-shutdown - but that said I don't have my Air yet...

 

[DJGuy]

I think a lot of people are mistaking single-core apps as a core-shutdown - but that said I don't have my Air yet...

Alan, you've hit the nail on the head. You can see a single core app running, and this is normal, if not the best programming. It's only when a core shuts down from overheating (or some other reason?) when you have a problem. I've definitely had this happen, but like other people here, it's not frequent and it's hard to reproduce the conditions. For me, most of the time the Air is running great and I'm very happy with it.

 

[ChrisA]

It's only when a core shuts down from overheating (or some other reason?) when you have a problem.

The other reason the shut down a core is to save battery power. When the machine idles with nothing to do it can un-power one of the cores.

Some computers (I don't know about the MBA) can change their clock frequency to run slower when there is little to do.

I imagine that the MBA likely was a self-protection mode such that when it gets to hot it goes into one of the power saving modes that was designed to save battery power but does double duty as a heat relief mode.

The problem here is not one that is easy to solve. A notebook computer is basically just a battery and a 25 watt heater inside a closed box. So what to do about the heat. There are only a very few options that the laws of physics allow.

1. Pull cool air into the box, heat it then send it back out.
2. Heat the case itself and let the hot case act as a radiator
3. Run the 25 watt heater at a low setting to uses less power

I don't think there is an other option. Normally notebooks use a combination of all three. But Mac users will while about each of these

 

[Alan Taylor]

I don't have my Air yet, so I don't have any experience of one, but when a 'Core Shutdown' happens, does the core ever come back to life? If so the heat-saving theory would hold a lot of water. It may well be that your Air is generating *too much* heat for it to happen so easily, but I'm not sure at this point that these are caused by faulty CPU's...

 

[Sesshi]

I think a lot of people are mistaking single-core apps as a core-shutdown - but that said I don't have my Air yet...

I don't doubt it, especially with many being easily-led Mac users as soon as they latch onto a potential problem they're ill equipped to even start to diagnose.

That aside, what some of us are experiencing may not necessarily be a core shutdown, but nevertheless there are definite pointers to the CPU, GPU or chipset being put in a state of thermal protection at certain times where neither the environmental or usage scenario logically lends itself to such a problem. The stuttery overall response not consistent with application or OS issues is one of those examples.

 

[deputylove8]

I want a real working comp! Hehe. Mine dies and gets mega hot! Haha

 

[ayeying]

It seems like the chipset controlling the entire funtions of the mobo is causing the CPU core to shut down.

Think about it, if it was heat related directly to the CPU, wouldn't ALL core 2 duo have this feature. Furthermore, I have run this CPU in the excess of 100 deg C (yes, I know, its a little hot) and the core did not shut down, further explains it is not directly related to the CPU but the chipset

 

[Alan Taylor]

I wonder if the writing of a small, simple app that will put a small load balanced across all avalible cores will help identify if the core has shut down or not.

If so, we could run this durin a 'core shutdown' and see if the core is just being ignored by the other apps at the time, or if it really has shut down.

Ideally it would have a basic GUI to report back how many cores it had access too...

Once I get mine I will have a play around with Xcode and see if I can knock something together - in the meantime I am sure someone more capable than I could come up with something too!

 

[J&JPolangin]

...Some computers (I don't know about the MBA) can change their clock frequency to run slower when there is little to do....

...my old Sony Vaio TR-3A changes freq at times (and its a 5+ yr old) sub-3 lb machine...

 

[sanPietro98]

If I only look at the Activity Monitor's history graph, I sometimes see that Core #2 has no activity when (at times) when watching videos for extended durations.

But even when it does that, I don't notice any performance difference in the machine. No video stuttering. No mouse jitters. I wouldn't even suspect it were it not for the Activity Monitor.

If that's a core shutdown, I'm ok with it.

I'm running 10.5.4 with all the latest firmware. I do not use CoolBook.

 

[yoavcs]

The OS will always utilize both cores, so even if you are running a single-threaded app you'll see both cores running, unless the CPU is in a power-saving state or core-downing (heh, new phrase).

The Air's cores don't shutdown due to overheating of the CPU. You can easily ramp just the CPU up to close to 100C and not see a shutdown.

What is happening is that the Air's chipset is inadequately cooled. When it gets hot the entire system clock is brought down and a core shut to keep things cool. That is why you get jittery performance. You essentilly have a single-core 800MHz CPU with a slow bus and slow chipset all running off a slow clock.

Things that can cause the chipset to overheat? Graphics, large data transfers (such as USB) etc...

The Air's chipset is not adequately cooled and I hope Apple remedies this by the Air 2.

 

[DJGuy]

The OS will always utilize both cores, so even if you are running a single-threaded app you'll see both cores running, unless the CPU is in a power-saving state or core-downing (heh, new phrase).

The Air's cores don't shutdown due to overheating of the CPU. You can easily ramp just the CPU up to close to 100C and not see a shutdown.

What is happening is that the Air's chipset is inadequately cooled. When it gets hot the entire system clock is brought down and a core shut to keep things cool. That is why you get jittery performance. You essentilly have a single-core 800MHz CPU with a slow bus and slow chipset all running off a slow clock.

Things that can cause the chipset to overheat? Graphics, large data transfers (such as USB) etc...

The Air's chipset is not adequately cooled and I hope Apple remedies this by the Air 2.

Somewhere, I posted, I think in a poll, that I made my core come back to life by blowing into the 789 side (the right side) of the grill. This was actually repeatable for several times on the one day that this happened. Eventually I switched to fanning it with a folder so I wouldn't hyperventilate. I picked the right side because the warm air seemed to be coming out of the left side, and I couldn't see any other air inlet.

If this really does work, then someone can come up with a third party solution, like they did for the old Mac Plus.