Amstrad Plus

Released in late 1990, the Amstrad Plus range is an update to the earlier Amstrad CPC. In order to preserve compatibilty, it uses the same CPU (4MHz z80) and RAM size (64 and 128K models). The Plus boots in CPC-compatible mode, and the new features are not available until a secret unlock sequence has been sent to the ASIC chip. The idea was to sell this unlock sequence only to game manufacturer who would distribute games on cartridges - targetting both the Plus computers and the GX4000 console. However the unlock sequence was leaked from Amstrad, allowing demomakers to use the new features.

Those features include a 4096 color palette, 16 hardware sprites with a separate color palette and 3 zoom levels, hardware scrolling and automated screen splitting, a rasterline interrupt and 3 DMA channels feeding the AY3 sound generator. These features makes the hardware rather complex and the ASIC chip is known to have several rather annoying bugs which adds to the challenge of writing a demo for the platform.

Thanks to Pulkomandy for this platform description, and the picture!

Emulators available for this platform includes;

WinApe