On my former assembler days, using different register banks helps to make code impressive smaller and faster.

E.g. I used R0 and R1 of bank 1 to hold directly the transmit and receive buffer pointer for the UART interrupt.
And the remaining adresses R2..R7 (0Ah..0Fh) are still free as SRAM.


But on C programming I detected mostly larger code and more SRAM usage.
It seems, that C can not be forced to hold global variables in registers.

Also watch, that some mathematics already occupy a second register bank.

So my conclusion, using "using" was only helpful in assembler.


Peter