Internal 512 KB RAM expansion for CPC6128 from german magazine '''c't, issue 10/1987'''. The DIY project name is '''CPC 6512'''. One half The mod requires to remove (256Kor disable) of the total (512K) expansion memory can be accessed as Video sixteen RAM (with normal expansionschips on the CPC6128 mainboard, only 64 KB are accessible as Video RAM). The c't expansion is compatible with [[Standard Memory Expansions]]and to replace them by bigger chips, and provides the plus whatever additional CRTC feature, but it misses 64 KB usually addressed via I/O ports &7FFC, &7FFD, &7FFE and &7FFFbank selection logic.
One issue later, c't 11/1987, the magazine published a driver which creates a RAM disk within the additional memory. This RAM disk can be used in [[AMSDOS]].
== Technical ==
I/O Ports are &7FC4The memory is accessed via Port 7Fxxh, &7FC5as on [[Standard Memory Expansions]].Since the internal RAM is removed, its total capacity is only 512K (unlike standard 512K expansions which provide 64K internal plus 512K external memory, ie.576K total).&7FF7Altogether, the c't expansion works like a 448K dk'tronics expansion (leaving the banks selected via OUT [7Fxxh],FCh. &7FC0 selects .FFh unused). One half (256K) of the first total (512K) expansion memory can be accessed as Video RAM (with normal expansions, only 64 KBare accessible as VRAM). With this This is making the expansion slightly incompatible with the CPC can access 512 KB RAM totaldk'tronics standard. With a "normal" 512 KB However, usually expansion memory is mapped to 4000h-7FFFh, whilst VRAM is usually mapped to C000h-FFFFh. So, most existing software may work with it can access 576 KB , without accidently displaying garbage on the screen. == Missing Info == * Unknown which banks are usable as VRAM** The first four 16K bank are (64 KB probably) usuable as VRAM (as on all 64K CPC models)** The next four 16K bank are (hopefully) not usuable as VRAM (for CP/M+ 512 KBcompatibility, which uses them as Work RAM)** For further banks it's totally unknown if they are used as VRAM or not* Unknown if it's fully dk'tronics compatible, or more like incompletely implemented Inicron variant* Unknown what happens on accessing the unused region via OUT [7Fxxh],FCh..FFh* Chipset / Schematic is unknown
== Scanned Article / Schematics ==