Standard Memory Expansions

The standard expansions are based on the RAM banking logic from the CPC6128, ie. equivalent to the fourth Gate Array register in the CPC6128 (or more precisely, the PAL that assists its Gate Array chip).

• Accessing a 64K expansion (or the first 64K of a bigger expansion) is compatible to the 128K in the CPC6128
• Although, for real CPC6128 compatibility one may need some patches (eg. CP/M Plus refuses to work without the 6128s BASIC version) (it "detects" the 128K by checking the BASIC version)

Expansions bigger than 64K combine the CPC6128-style mapping with some formerly unused chips in the fourth Gate Array register:

Capacity

• A nnK expansion adds nn Kbytes to the internal 64 Kbytes in the CPC. So the resulting size is nn+64 Kbytes.
• This does in most or all cases also apply on the CPC 6128: only 64 Kbytes of it's internal memory are used (the 2nd half of internal memory is disabled and replaced by the expansion RAM, the resulting size is nn+64, not nn+128 Kbytes)

Standard Expansions

• Dk'tronics memory expansion - 64K and 256K expansions