Why does ambient temperature matter for laptops?

What is the danger of using a laptop when the ambient temperature in the room is too high? Is it that it makes it harder for the fans to cool the machine?

Considering that, from what I've been reading, the core of a laptop can get into the mid-100s (F), it wouldn't seem that the temperature of the room being 95 or 100 F should be an important factor at all. Yet the manufacturer of mine (Dell XPS 1530) recommends a maximum operating temp of 95 F.

 

You're correct. The reason is because it is harder to keep the system cool. If you're in a room that's 100 F than you system won't be cooler than 100 F and would be a lot higher than that even. If a laptop can hit 80C in a room of 'normal' temperature, imagine how hot it would be in 100F.

 

Thanks for that info. I've been concerned because I stupidly started up my laptop in a very warm room (about 100 F) a few days ago. The laptop itself had been stored in the same room, and was as hot or hotter (very warm to the touch). I didn't do anything but web surf and e-mail, but later I realized that I might have damaged the machine by not letting it cool down, and letting the room cool down, before starting the laptop (Dell XPS 1530.)

 

The system will downclock or shut off before it can do any hardware damage. Running it on high temps will just slowly reduce its long term lifespan.

For your instance, i wouldnt worry about it. Just try avoid it if you can.

 

A 5° higher ambient temp translates directly into 5° higher CPU core temp. That's how thermal conductivity works:
http://en.wikipedia.org/wiki/Thermal_conductivity

The difference between the cool and the hot item (= delta temp) stays the same. If you raise the cool part (= ambient temp) than the hot part (= CPU) will get a higher temp by exactly that amount.

If you don't like wikipedia, you may also check intel's specification. E.g. the Pentium MMX processor p.46 section 5.1 "Measuring thermal values":
http://datasheets.chipdb.org/Intel/x86/Pentium MMX/24318504.PDF

There is a formula (which is basically the same as on wikipedia):

T A = T C - (P * Theta_ CA)

P = power consumption of the CPU
Theta_ CA = your cooling solution
T A = ambient temperature
T C = CPU case temperature

If you raise T A, then T C will raise by the same amount.

 

The ambient temp is the baseline temp and the CPU and other temps will be relative to that. Also it's the ambient air you are using to cool and exchanging with so the machine wont be cooler than the surrounding air.

Any system involving air cooling is limited by the ambient temperature - not just laptops.
You car engine will run hotter with a hotter ambient temperature.