View source for 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:

Gate Array, Port 7Fxxh:
  7-6  Must be 3 (aka Gate Array Register 3)
  5-3  Bank number in 64K units (for expansions bigger than 64K)
  2-0  Bank mapping in 16K fragments (as on normal CPC 6128 Gate Array)
The 16K fragments are consisting of 8 banks. Banks 0-3 are the internal RAM, banks 4-7 are external RAM (taken from the currently selected 64K block).

== 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
* [[Dobbertin Memory Expansion]]
* [[CPC4MB]] (DIY) - compatible with standard 512 Kbyte expansion (plus extra non-standard 3.5 MBbyte)
* [[RAM BOX]] 512Kb memory expansion '''(is that lowercase "b" meaning 512kbit=64Kbyte ???)'''
* The first 192K (of total 512K) in [[Aleste 520EX]] are standard compatible

== Non-Standard Expansions ==

* [[Inicron RAM-Box]] - not fully compatible with standard expansions
* [[Otten & Fecht 1 MB RAM-Disc]] - Accessed through I/O ports (RAM is not mapped to memory)
* [[Vortex Expansions RAM card]] - non-standard

== Expansions that are unknown how they work, and if they are standard or not ==

* [[RAM7 2Mb memory expansion]] - is that 2Mbit or 2Mbyte? what I/O ports would be used to access 2MByte?
* [[Inicron RAM-Box]] - not fully compatible with standard expansions
* [[Data Media SP64]] - all unknown
* [[Dk'tronics Silicon Disc]] ([[Dk'tronics]]) - all unknown
* [[Phoenix M64]] - all unknown