Yes, I know that Apple has thoroughly tested their products and running a CPU at 90-95 degrees and a GPU at 75-80 degrees is perfectly safe, and that high fan speed will not significantly lower the lifespan of the fans, and that usually there is no reason to worry about temperatures. However, there has recently been a worrying change, for no apparent reason, in the thermal performance of my computer, which is what this thread is about. When I first got my late-2013 15'' rMBP, the CPU temperatures would regularly exceed 90 degrees Celsius and the GPU would stay nicely under 80 degrees, usually with quite slow fans (3000-4000 rpm). Occasionally, when needing to complete intensive tasks on battery, or when doing long intensive tasks in the background and not wanting to hear the fans all the time, I would use Turbo Boost Switcher to turn off turbo boost on the CPU - this would keep my CPU temperature at around 70-75 degrees and the fans off. Recently, however, I have noticed something strange. First of all, the CPU temperature never rises above 80. Never. I even tried running Prime95; the overall CPU temperature (which smcFanControl shows) never went above 75 degrees Celsius, though the individual CPU cores were in the 94-98 range according to iStatMenus. Previously smcFanControl would show 90-95 degrees for the overall CPU and the cores would be at 95-100 degrees. Now, cooler temperatures are always better, but this is confusing. Perhaps Turbo Boost Switcher permanently stopped the CPU turbo boost for some reason? The worrying part is that the GPU temperatures have suddenly taken a rise. Previously it was difficult to get the GPU temperature over 80 in anything; now it will easily stay in the 84-86 degrees range even with the GPU fan at full speed (5700 rpm) when playing games. However, for some reason the Unigine Heaven benchmark, which makes the whole computer sluggish, will not raise it further than 80. Also, even when only the iGPU is running, the GPU temperature heats up faster than the CPU. Why is this? Perhaps I'm overthinking things, but this seems very strange to say the least. So to summarise, my questions are: 1. Is running a GT 750M at up to 85-87 degrees Celsius several hours a day going to significantly affect the system's lifespan or cause damage? I intend to keep this computer for a long time. 2. Is there a free Mac application that lets me see the CPU's clock speed to ensure that turbo boost is working as intended? 3. When people talk about CPU temperatures, are they talking about the core temperatures or the overall CPU temperature (what iStatMenus calls "CPU Proximity"