The ZX Spectrum Next use bank switching to allow the processor to access the physical memory beyond the 64KB that an 8-bit processor with a 16-bit address bus would normally be able to access. Here's a quick peek at the concept as well as a look at a new system variable MAXBNK.

ZX Spectrum Next User Manual:
https://archive.org/details/zx_spectrum_next_manual/mode/2up

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