Difference between scratch/scratch_fast area?

I’m using U55.
Looking at the code and generated command stream,
flash area is area 0
scratch area is area 1
scratch_fast area is area 2

And I don’t see “scratch_fast” actually used in the command stream.
Is scratch_fast only used in U65?

@slhskgsdlfjslg yes, fast_scratch is used only for U65 for spilling of feature maps between DRAM to SRAM. Actually, this is for the case when both model and arena are placed in DRAM and we use internally scratch_fast_tensor allocated in Tensor Arena, and then this address is exchanged by TFlM/Driver to point to the fast storage memory SRAM to make the inference faster.