This article describes device specifics of the Silicon Labs EFM32 series devices
Auto SWO speed calculation of J-Link does not work for the Silicon Labs EFM32 series devices.
Normal SWO Speed calculation: <CPUFreq> / n
EFM32 specific:Chip-internally wired to a fixed 14 MHz clock (AUXHFRCO)
For utilities like J-Link SWOViewer or similar: Select 14 MHz as CPU speed (no matter what the CPU is really running at) to make the normal calculation working