Hacker News Reader

Comment by josephcsible | Hacker News Reader

> My point is that laptops with 90W adapters can get too hot to comfortably touch, I think at 180W you're well past the point where actually using it on your lap is advisable.

You're mixing up thermal energy and temperature. Consider that you can easily burn yourself on a 60W soldering iron, but it'd be quite hard to do so on a 1500W oil-filled space heater.

View on HN

You could keep temperature down with fans, but my 90W thinkpad has fans so strong it sounds (and feels) like a hair drier and still runs very hot. I'm having a hard time imagining a 180W laptop that isn't hotter than hell.

You have a gap in your understanding of the physics here. Even a 400W laptop can be cool to the touch.

A laptop is hot to the touch because it has hot components (eg a processor running at full throttle) and fails to dissipate that heat correctly.

That is mostly divorced from it's power consumption.

If you ran a large robotic arm off your laptop, you'd be using a lot of watts but making only a bit of heat.

There's no gap in understanding, the only way a 400W laptop can be cool to the touch is if it rapidly dissipates all that thermal energy. That would require one hell of a fan, which is what I said with my hairdrier remark. Even 90W already requires a very noisy fan. A fan moving enough air to keep a 400W laptop cool to the touch isn't realistic to put into the form factor of a laptop, and a fan sufficient to keep even a 180W laptop cool seems extremely dubious to me. It would sound like a vacuum cleaner.

What I was missing is the part where the laptop doesn't consume 180W and a substantial fraction of that power is just passing through the laptop to peripherals.

Case in point, I’ve driven my desktop computer up to 600 watts and mostly it just puts out a warm stream of air silently.

You’re missing another variable here. In your case it may just be the thermal interface material (TIM) isn’t doing a good job of transferring the heat from the processor onto the heat sinks that the fan blows over.

I’ve had temperature drops of over 15 degrees c by opting for Liquid Metal, everything else being same.

Additionally, loudness is not necessarily correlated with actually moving air. It can often correlate with obstruction to moving air.

Reply on news.ycombinator.com