ZX Spectrum Memory Banking

The Spectrum Next comes with 1 or 2 megabytes of RAM, but being an 8 bit CPU the most it can address at any one time is 64K.

To get around this obvious limitation the RAM is split into banks of 16K (or 8K if you use a different technique to the one shown here, look in the manual). The programmer can then choose which banks are mapped into the Z80’s address space by using special memory banking registers.