Teensy 4.1 features an ARM Cortex-M7 processor at 600 MHz. Actual size is 2.4 by 0.7 inch, same form-factor as Teensy 3.6. Teensy 4.1 uses the same processor as Teensy 4.0, but provides greater I/O capability, including an ethernet PHY, SD card socket, and USB host port. Teensy 4.1 also comes with 4X larger flash memory, and has 2 locations to optionally add more memory.
The ARM Cortex-M7 brings many powerful CPU features to a true real-time microcontroller platform. The Cortex-M7 is a dual-issue superscaler processor, meaning the M7 can execute two instructions per clock cycle. Tightly Coupled Memory is a special feature which allows Cortex-M7 fast single cycle access to memory using a pair of 64 bit wide buses. Teensy 4.1's Cortex-M7 processor includes a floating point unit (FPU) which supports both 64 bit "double" and 32 bit "float".
When running at 600 MHz, the Teensy 4.1 consumes approximately 100mA current and provides support for dynamic clock scaling. If a coin cell is connected to VBAT, Teensy 4.1's RTC also continues to keep track of date & time while the power is off.
More information is available on the website of PJRC.