M33 core is an improvement of M4 core, for official comparison se here.
Below there is a quick comparison.
Key features of the Arm® Cortex®-M33 core (form ARM web page)
- Cortex-M33 is an implementation of the ARMv8-M architecture. Full details are in this blog on the 5 key features of the Cortex-M33
- Using the same debug interface as the other Cortex-M processors
- Offering the same functionality of a wake up interrupt controller for low power operation
- Implementing the same DSP/SMD instructions as the Cortex-M4
- Implementing the latest FPU specification which adds more instructions beyond what Cortex-M4 has
- Using the AHB5 specification for the system and memory interface to extend security to the whole system
- Using the latest version of the memory protection specification to simply the setup of regions
- Extends the number of maximum interrupts to 480
- An updated embedded trace macro cell to fit the processor design
- A micro trace buffer as an option to trace into memory instead of out to the trace interface
- Updated debug components that enhance debug operations and simplify usage
- A co-processor interface that supports up to 8 co-processors
- Stack limit checking in hardware
- TrustZone for software and hardware isolation