STM32F105
The original Gotek microcontroller. A lot of online documentation, for example describing how to flash a Gotek, assumes this chip and may not be directly relevant to more recent models. This MCU runs at 72MHz and has 64kB SRAM. It is enough for reliable emulation of most disk types, including high-density HFE disk images, on a wide variety of host systems.

Due to lack of availability, the STM32F105 has not been used in Gotek production since early 2021.