What is the significance of thermal calibration? T-Cals, as they are commonly known (see WFTD archive Thermal Recalibration), have historically been a necessary evil in hard disk technology. The software in a hard drive had to periodically adjust the operating parameters of the drives as they became heated. In order to accomplish this a drive would have to momentarily stop reading or writing and go through a recalibration routine. Though this routine would only take a fraction of a second, that could be enough to cause a glitch in the playback or recording of digital audio. This was a very common problem in the early 1990's when hard disk recording systems were just getting popular. Later, many drives had intelligent enough software to wait until a read/write cycle was complete before recalibrating. This was a big help, but still sometimes errors would occur as the drive warmed up during an extended read/write without being able to recalibrate. Nowadays embedded servo (see WFTD above Embedded Servo) technology is employed to overcome this problem.