In Why Heat is the Enemy of Server Farms and Sometimes Less Power Means More, Cringely writes:

For a few years back in the early 1980s, I had in my cellar a Digital PDP-8 minicomputer. Didn't everyone? I bought the computer from a college for one dollar, and my labor to remove the thing from their computer room. Once set up in the cellar, I ran cable and put ADM-3A terminals in every room. This was years ago, but my clearest memories of that old PDP-8 were toggling-in the boot loader from memory IN THE DARK following several power outages and one earthquake. Oh, and the machine raised the ambient temperature in my house about five degrees. That box put out a LOT of heat, and heat is the topic of this column. It is the enemy of big server installations, the bane of blade servers, and there are times when heat turns computing economics on its head and makes it smart to use computers that are less powerful, not more.