With the same CPU, does a fanless machine run slower than one with a fan?

Under light and moderate load there is almost no difference. The gap only appears when the CPU runs hard for long periods in a hot environment. Modern CPUs throttle automatically when they reach their thermal limit. A fanless machine dissipates heat through its aluminium housing, so cooling capacity is limited: most fanless machines use CPUs with a TDP of 6 to 35 W, and some larger-housing lines can handle up to 65 W. If your software runs the CPU at 100% for hours at 50 °C, a fanless unit may sustain lower performance than a fan-cooled one with the same CPU. How to check before buying: 1. Read which CPU the published temperature range applies to and whether throttling conditions are stated. 2. Run your real software on a sample machine and log CPU temperature and frequency for a few hours. In return, a fanless machine has no fan to fail and draws no dust inside, so in a dusty workshop it usually lasts noticeably longer.