What happens if you cover the rMBP vents, such as sitting it upon a bed?

Discussion in 'MacBook Pro' started by Siderz, May 8, 2013.

  1. Siderz macrumors 6502a

    Nov 10, 2012
    I don't own an rMBP, not planning on getting one either, I'm just curious as to how big of a deal it would be to cover the vents on the bottom sides, it seems so prone to being covered if you sit it on a bed.

    Also I have an 11" MBA, if I sit that on my bed, does it still ventilate from the top of the vents or does it get most of its ventilation from the bottom most side of the vents?

    Maybe I'm not being clear, I'm a bit sick today, I'm just curious as to how the vents work on MacBooks, would be cool if someone could produce an illustration.
  2. F1 Fan macrumors regular

    F1 Fan

    Apr 18, 2012
    The intake vents on the rMBP are on the sides and slightly underneath the machine. The air then gets moved through the internals and out through the vent at the back and upper edge of the main body, just below the display.

    Placing the rMBP on a soft surface like a pillow or duvet can easily block the intake vents. That means that however much the fans spin, no cool air can come into the machine and heat will begin to build. There's no problem with this provided you're not letting too much heat build.

    The instructions actually warn against using it on a bed or similar surface.

    Not sure about the vents on the MBA
  3. yvonnars macrumors newbie

    Nov 30, 2012
    it gets really hot

    I just did this 5 minutes ago before I read your post and I have the answer you want.

    I have a 15in rMBP early 2013 edition, I just turned it on when I got home, left it on my bed with charger plugged in (using AC adapter power), replied to a text I got which took few minutes, and when I picked up the comp again and put it on my bare legs, it nearly burned me. I then checked in force application quit window (cmd+option+esc) comp has nothing running except finder. Checked istats excpt for HD everything else was about high 40 to low 50 degrees, and GPU diode about 65 degrees.

    Now I just checked again everything is at about high 30 to low 40. I'm not sure if this is normal temp tho
  4. ColdCase macrumors 68030

    Feb 10, 2008
    Much of the internal heat flows out through the back cover as well as the vents, and putting a laptop on an insulating surface will adversely affect cooling. I would worry more about that than venting. A Mac will shut down before it gets hot enough for damage.

    So laying the laptop on a bed will adversely affect cooling, the Mac will run hot and perhaps get to the point of shut down.
  5. pgiguere1, May 8, 2013
    Last edited: May 8, 2013

    pgiguere1 macrumors 68020


    May 28, 2009
    Montreal, Canada
    Well it will get hot as expected, but won't cause damage to the Mac itself. You'd be blocking the air intake meaning the cooling wouldn't be very effective.

    The CPU will simply be throttled down so that the Mac doesn't get hot enough to be damaged. Even if you forced it to get even hotter it would just shut down at some point to prevent damage.

    So it's really a matter a comfort and whether or not you can tolerate the heat. If you're just web browsing or doing a similar light task, it will barely get hot at all. If you're gaming or doing something else intensive, expect weaker performance because of the throttling.

    I used to have a 2011 1.8Ghz i7 11" MBA, and my 2.6GHz 15" rMBP is definitely a lot cooler when used on a bed. My Air was getting so hot that I stopped using it in bed even for the most basic stuff, while my rMBP is completely fine as long as I'm not doing anything too intensive. I never noticed if the air intake vents are blocked or not while it's sitting on my bed but either way it doesn't seem to cause too much problem.

    Here's for the illustration you asked (not mine) :

  6. emptysoul macrumors regular

    May 26, 2009
    Mine has been sitting on my bed for the last few hours and temp is only at 45C with fans at 2000rpm.
  7. johnnnw macrumors 65816


    Feb 7, 2013
    If I'm not at school I'm using my laptop while it's sitting on my bed, never go above 50 degrees and always around 2000rpm.

    It's no problem.

    My old HP laptop relied on a bottom vent, I still used it on my bed all the time although is got extremely hot.
  8. Siderz thread starter macrumors 6502a

    Nov 10, 2012
    Oh wow, thanks for getting that illustration, I just noticed there's a sort of gap for air to flow more easily through the vents, I didn't notice those before, I had the weird idea that the cool air would go over the batteries...which would make it warmer, had me confused there, that would be like when people have water cooling go from the radiator, to the CPU, to the GPU, and back to the radiator.

    Also, the people saying that the Mac will shutdown before the temps can begin to cause damage, does that pretty much mean I could play Minecraft on my MBA all I want as long as it doesn't shutdown? Because I'd sometimes play Minecraft on my MBA, and the fans would go up, I'd get scared, and I'd give it a rest. I think the temps start to go up to something like 80°C.

    I don't really play Minecraft often, and at home I can just play it on my iMac, but it would be a relief to know that I haven't drastically shortened the life of my MBA by playing Minecraft every so often.

    Edit: Another question, does the cooling on the 15" MBP include the discrete GPU? Looks to me like the GPU is just below the RAM and has no fan.
  9. B... macrumors 68000


    Mar 7, 2013
    80 degrees is normal while gaming. The Mac shuts down near 105-110. You can play as long as you want, just do not play at 105 degrees for four hours. You will hurt the lifespan of the computer if you do so.
  10. pgiguere1, May 9, 2013
    Last edited: May 9, 2013

    pgiguere1 macrumors 68020


    May 28, 2009
    Montreal, Canada
    It does. The GPU is in between the two fans and there's a heatsink on top that transfers the heat to the fans. I circled it in this picture and tried to illustrate the heat transfer:

    You can see the GPU better here:

    The other chip in the middle is the CPU.

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