But running at higher clock speeds increases temperature. Has Apple ever yet said what the clock is for the various systems? I'm sure a notebook is going running slower, cooler, leaner power wise than a desktop version of the same chip which can obviously run faster, warmer, and unbridled by battery life concerns. So if the SOC runs hotter, the memory is going to run hotter too. 'Free space' in the chassis also plays into cooling. The Mac Pro should cool better than the Studio/Mini. It's just 'bigger', and dumps more air through that cavernous enclosure than a notebook, or Studio/Mini. I'd therefore expect the new Mac Pro to run faster (hotter) than earlier iterations of the same basic technology because it can breath better, has room for bigger power supply and NEEDS to be fast, 'pedal to the metal', along with all (most) of the other stuff in the box. So size of heat sink, but also how easy it is to get cooling into the box. Air cooling a fast Ultra alone wouldn't seem to make sense. Heat sinks and fans are far more efficient at removing heat. I'd expect the new Mac Pro to have some pretty interesting thermal management gear stuffed in the box.