| 6 || 1
|-
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| 5 || - b || rowspan="3" |not used (or 64K bank for number (0..7); always 0 on an unexpanded CPC6128, 0-7 on [[Standard Memory Expansions]])
|-
| 4 || -b
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| 3 || -b
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| 2 || x || rowspan="3" | RAM Config (0..7)
The 3bit RAM Config value is used to access the total second 64K of the total 128K RAM (RAM Banks 0-7) that is built into the CPC 6128or the additional 64K-512K of standard memory expansions. These contain up to eight 64K ram banks, which are selected with bit 3-5. A standard CPC 6128 only contains bank 0. Normally the register is set to 0, so that only the first 64K RAM are used (identical to the CPC 464 and 664 models). The register can be used to select between the following eight predefined configurations only:
-Address- 0 1 2 3 4 5 6 7