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I have a weird problem on my 2011 MacBook Pro 15" running OS X 10.8.2.

Every now and then - say every two days - the system starts to ignore most of the keys I press for 2-3 minutes. It's like processing of keystrokes becomes incredibly slow. If I wait for ten seconds between each key, what I type is processed completely; otherwise kys wl b msng rndomly.

The system is not overloaded in any way when this happens. I'm usually writing something and this comes out of the blue.

Has anybody experienced the same, or could point me to some resources? I'm having a hard time coming up with a good Google query for this problem.

It is possible this was introduced by the 10.8 upgrade but I'm not 100% sure.

Edit: so I managed to run top while this occurred again and the only thing that was runnng that usually isn't is Google's ksfetch. Will post more info if I catch it again.

share|improve this question
have you tried reading the system log and finding if at that time happens something weird? and are you having that when in the Mac locally or remotely? (this happens to me remotely and sometimes when the mac is in a lot of stress). Thirdly, have you had the luck to have the activity monitor open when that happens, and see what may be causing that? Finally, has that happened to you always, or recently? (this would mean an app/launch daemon or similar could be the reason) – jackJoe Feb 9 '13 at 11:32
I second @jackjoe's recommendation. You can access the system log files by opening the Console app. (Type Console into Spotlight). If you open it, you will see a list of messages scrolling in real time. Keep it open, and have a look at the messages from just before this happens. – daviewales Feb 9 '13 at 13:09
@davie neat, will do and report back if I see something, thanks! – Pekka 웃 Feb 9 '13 at 13:56
Have you considered this to be a hardware issue? .. If you plug in an external USB keyboard, does the same issue occur at the same rate as the onboard? – adamrmcd Feb 9 '13 at 21:31
I am having exactly this problem, at exactly the same sort of rate (every two days or so, lasting 2-3 minutes) on exactly the same machine/OS. Weird. It's definitely not a hardware problem with the keyboard, because (a) it just lasts for a few minutes, and (b) there's a delay of ~1 second between pressing a key and seeing the character appear on the screen, and it seems that any other keystrokes during that delay are lost. @Pekka웃 did you find anything from the logs? – callum Feb 15 '13 at 13:42

This is most likely caused by the CPU being overloaded, so the kernel is throttled. That means only number of samples that are processed for a specific period to avoid overheating to prevent the crash.

To confirm that, run the following command in Terminal:

sudo fs_usage | grep -v 0.00

which should show something like:

THROTTLED  0.015030   kernel_task
THROTTLED  0.019601   coreduetd
THROTTLED  0.031014   kernel_task 
THROTTLED  0.014947   kernel_task

which means your kernel being throttled which may result in such unexpected behaviour (see also: Why kernel may be throttled?).

I had this problem when my system was eating t letter (for all the apps) and CPU sensors (in iStat) were over 90˚

To solve the problem, check the above command fs_usage and kill unnecessary processes. If it's web browser with too many tabs and a lot of ads and JS scripts in the background, close unnecessary tabs.

There is also a chance that it's caused by I/O throughput (disk access) and your storage (e.g. SSD) may be reaching its lifespan.

share|improve this answer
Cool. The problem hasn't reappeared since but I'll be looking for these if it happens again! – Pekka 웃 Jun 20 at 11:34
I had this problem today and every second day and as result it's eating t letter quiet often for all apps. I believe it's overheating (on iStat it's showing over 90˚), because when the system works normally it works fine. The only part I don't understand why it's always eating t in my case. – kenorb Jun 20 at 12:13

FWIW: I'm having the same problem on my late-2011 11" MacBook Air. Every now and then some of the characters on the keyboard will simply stop responding.

My current theory is that it is a problem with overheating, because it only happens when using the laptop keyboard (and never with an external keyboard) and it only happens when the laptop is actually on my lap and never when it is on a desk or table or other flat surface with adequate ventilation.

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Let's see whether somebody else can confirm your theory about the overheating. – patrix Jun 16 '13 at 7:37
Mine is doing it without any overheating. (Retina, 15-inch, Early 2013) – KARASZI István Jul 24 '13 at 9:24

The internal keyboard is actually on USB. This suggests something else is hogging the USB. On my Retina MBP the other thing on that bus is the Bluetooth controller.

  1. Any other USB peripherals? iPad or iPhone connected?

  2. Anything hooked up on Bluetooth? Mouse perhaps?

  3. Any errors for either of the above in Console? Any other high frequency errors?

  4. Go to System Preferences -> Accessibility -> Keyboard and confirm that Sticky Keys and Slow Keys are off.

There was a spate of reports of similar problems around 2009 which I think were fixed by a Keyboard Firmware upgrade, but that should be bundled with 10.8. Sorry I can't find a conclusive answer in this case.

share|improve this answer
Interesting. I think I have observed this with no USB devices connected, but I'll keep an eye on it. – Pekka 웃 Aug 13 '13 at 12:32

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