On Feb 17, 2011, at 8:56 AM, Scott Matthews wrote: > ? Those are the processor options listed for X201's on the Lenovo site, and > so I was trying to get a sense for how they compare with respect to heat > output, because I don't like it when my laptop gets hot and noisy. Why is > that vanity? >
Scott, What you need to compare is the Thermal Design Power - Intel rates that for mobile CPUs. It can vary widely - some old P4 mobile chips were over 80 watts and an Atom is less than 10. Some old low power Pentium M versions were below 1 (yes ONE) watt. Current i7 quad cores are about 45 watts. Of course, the CPU will draw much less than TDP most of the time as things can be throttled/shut down but the higher the TDP, the bigger the heat sink/fan required to keep the CPU under the max allowed temperature when running at full tilt. One other thing to consider - a separate GPU will add to the thermal load. In some cases, high performance GPUs such as the high-end Nvidia Quadros can draw MORE power than the CPU with both running at full power (they turn that large amount of electrical power into heat). High powers don't do much for battery run time either :-( Design of the thermal system can vary widely. Typically, high quality fans can be less noisy. Larger diameter fans running at slower speeds can move the same amount of air with less noise than high RPM, small diameter fans (if designed/built correctly). I'm not sure that most PC manufacturers consider noise very carefully when they design their machines. Sure would be nice if they provided noise levels at full power for notebooks :-) The two fairly large diameter fans in my year old 17" Apple MacBook Pro run most of the time but very slowly and quietly. The vent dumping the slightly warm air (unless the machine is really working) face to the rear and I cannot hear the two fans even in a quiet home with AC/heat air handlers off, etc. That was not true of my last ThinkPad that had a much lower power CPU (with lower TDP) but that had a single fan exiting to the side. The GPU in the ThinkPad didn't help matters either. When I replaced the ThinkPad fan, I noted that the heat sink contact area of the GPU was way larger than for the CPU - not a good sign for low thermal load. My MacBook has a switchable GPU - the high performance one causes the machine to run warmer to the touch and the battery won't last for 5 plus hours like it will with the lower power integrated graphics unit. Passive heat sink designs can work but they are typically MUCH larger and heavier than fan designs as the flowing air removes heat much more efficiently than convection. Some heat sinks are rated for both natural convection and with fans - the fans allow some heat sinks to get rid of 5 to 10 times as much heat for the same temperature rise. That is why you have at least one fan in most PCs whether they are notebooks or desktops or servers. I wasn't able to quickly find a table listing TDP for current Intel mobile CPUs but I found one some time back (now I wish I had saved a copy or at least a link). Stuart _______________________________________________ Thinkpad mailing list [email protected] http://stderr.org/cgi-bin/mailman/listinfo/thinkpad
