been triggered, thus preventing existing CPC software from accidentally invoking them. Despite the significant hardware enhancements, many viewed it as outdated, being based on an 8-bit CPU, and it failed to attract both customers and software producers who were moving towards systems such as the Commodore Amiga and Sega Mega Drive which was launched a few short months after the plus range. The plus range was a commercial failure, and production was discontinued shortly after its introduction in 1990. 464plus, 6128plus The 464plus and 6128plus models were intended as "more sophisticated and stylish" replacements of the CPC464 and CPC6128. Based on the redesigned plus hardware platform, they share the same base characteristics as their predecessors: The 464plus is equipped with 64 KB RAM and a cassette tape drive, the 6128plus features 128 KB RAM and a 3" floppy disk drive. Both models share a common case layout with a keyboard taken over from the CPC6128 model, and the respective mass storage drive inserted in a case breakout. In order to simplify the EMC screening process, the edge connectors of the previous models have been replaced with micro-ribbon connectors as previously used on the German Schneider CPC6128. As a result, a wide range of extensions for the original CPC range are connector-incompatible with the 464plus and 6128plus. In addition, the 6128plus does not have a tape socket for an external tape drive. The plus range is not equipped with an on-board ROM, and thus the 464plus and the 6128plus do not contain a firmware. Instead, Amstrad provided the firmware for both models via the ROM extension facility, contained on the included Burnin' Rubber and Locomotive BASIC cartridge. This resulted in reduced hardware localization cost (only some select key caps and case labels had to be localized) with the added benefit of a rudimentary copy protection mechanism (without a firmware present, the machine itself could not copy a game cartridge's content). As the enhanced V4 firmware's structural differences causes problems with some CPC software directly calling firmware functions by their memory addresses, Amstrad separately sold a cartridge containing the original CPC6128's V3 firmware. Both the 464plus and the 6128plus were introduced to the public in September 1990. Initial suggested retail prices were / with a monochrome monitor and / with a colour monitor for the 464plus, and / with a monochrome monitor and / with a colour monitor for the 6128plus. GX4000