Late 2013 15" rMBP throttling to 800Mhz at 70C/158F

[drecc]

I have a strange issue with my Late 2013 15" rMBP (i7 4960HQ - quad core base 2.6Ghz turbo 3.8Ghz):

Sometimes, under multicore load, my machine will slow down to a crawl.

According to iStatMenus, it is sometimes throttling the core frequency down from around 2.6Ghz to only 800Mhz when under multicore load. Throttling to 800Mhz doesn't happen under single core load.

This only happens when it is a little warmer than usual (it's happening right now, and the room temperature is 24C / 75F, which is warmer than usual where I live).

I'd understand if the CPU was getting too hot, but it's only running at 70C/158F (which is the reported CPU core 1 temp), which seems too low to cause the throttling.

Can anyone shed some light on this please? Thanks in advance

 

[Lennyvalentin]

Try opening the computer up and blowing it out with canned/compressed air, especially the heatsink. Note: don't use a vacuum cleaner, as this could kill your logic board due to ESD. Note 2: clean out the heatsink most efficiently by blowing air into it from the opposite direction fans normally push air through it.

If the heatsink is dusty, it will cause the fans to rev up, and if the fans rev up to max then the CPU will throttle instead when it gets hotter.

 

[drecc]

Try opening the computer up and blowing it out with canned/compressed air, especially the heatsink. Note: don't use a vacuum cleaner, as this could kill your logic board due to ESD. Note 2: clean out the heatsink most efficiently by blowing air into it from the opposite direction fans normally push air through it.

UPDATE:

Wow, this is fixed in a big way. I happened to have the right screwdriver, so I opened it up and sure enough, it was quite dusty. I duster sprayed it all out.

Now when I have all four cores under load, instead of staying at 70C and throttling them down to 800Mhz, it allows the CPU temp to get up to 98C at a frequency of 3.6Ghz.

This is very strange - I don't know why it didn't let the machine get to such a high temperature before, because that would have perhaps meant it didn't need to throttle.

Anyway, there is a night and day difference now so THANK YOU.

My only remaining question is: If my machine had been in warranty, would I have voided the warranty by opening it up to spray the fans clean? Can Apple tell that I've done this?

 

[Lennyvalentin]

I've actually damaged a thinkpad laptop about a decade ago by using duster spray on the fans. It caused the fan to fail, and I don't know why.

Possibly you blew dust/crud into the fan motor, and this jammed it, preventing it from spinning. Or you over-revved the bearings by blowing air at an unrestricted rate onto the fanblades (put a finger lightly on the motor hub to slow the impeller down when you clean it.) It's hard to say why, not having been there.

There's no particular reason compressed or canned air should be dangerous, used with some reasonable caution (like, not using such a powerful compressor that you risk actually blowing components off the boards and so on... ) It's how computers/electronic devices are cleaned out at any repair shop basically.

Before I attempt this though - should it be throttling at 70C/158F? If that is too low a temperature to be throttling at, then it doesn't seem as if cleaning out dust would make much of a difference?

Max core temps vary somewhat from CPU model to model. Also, the throttling behavior is programmable in firmware, so it's hard to say for sure why you're seeing what you see. The computer might be detecting if the fan/s are maxing out (or perhaps not revving up as high as they should, maybe due to worn or obstructed bearings) and thus throttling harder than it would have otherwise as a precaution, who knows. *shrug*

Opening the thing up and having a look would probably be a good idea to start with. At least if you don't have warranty coverage left. If you do, turning it in for service would probably be a better idea...

 

[drecc]

Possibly you blew dust/crud into the fan motor, and this jammed it, preventing it from spinning. Or you over-revved the bearings by blowing air at an unrestricted rate onto the fanblades (put a finger lightly on the motor hub to slow the impeller down when you clean it.) It's hard to say why, not having been there.

There's no particular reason compressed or canned air should be dangerous, used with some reasonable caution (like, not using such a powerful compressor that you risk actually blowing components off the boards and so on... ) It's how computers/electronic devices are cleaned out at any repair shop basically.


Max core temps vary somewhat from CPU model to model. Also, the throttling behavior is programmable in firmware, so it's hard to say for sure why you're seeing what you see. The computer might be detecting if the fan/s are maxing out (or perhaps not revving up as high as they should, maybe due to worn or obstructed bearings) and thus throttling harder than it would have otherwise as a precaution, who knows. *shrug*

Opening the thing up and having a look would probably be a good idea to start with. At least if you don't have warranty coverage left. If you do, turning it in for service would probably be a better idea...

I think I updated my last post after you already started replying. Just in case you didn't see it, thank you