Schneider Cpc 6128
Levi Satterley
The Amstrad CPC (short for "Colour Personal Computer") is a series of 8-bit home computers produced by Amstrad between 1984 and 1990. It was designed to compete in the mid-1980s home computer market dominated by the Commodore 64 and the ZX Spectrum, where it successfully established itself primarily in the United Kingdom, France, Spain, and the German-speaking parts of Europe.
The CPC models' hardware is based on the Zilog Z80A CPU, complemented with either 64 or 128 KB of RAM. Their computer-in-a-keyboard design prominently features an integrated storage device, either a compact cassette deck or 3-inch floppy disk drive. The main units were only sold bundled with either a colour, green-screen or monochrome monitor that doubles as the main unit's power supply.[2] Additionally, a wide range of first and third-party hardware extensions such as external disk drives, printers, and memory extensions, was available.
The CPC series was pitched against other home computers primarily used to play video games and enjoyed a strong supply of game software. The comparatively low price for a complete computer system with dedicated monitor, its high-resolution monochrome text and graphic capabilities and the possibility to run CP/M software also rendered the system attractive for business users, which was reflected by a wide selection of application software.
The philosophy behind the CPC series was twofold, firstly the concept was of an "all-in-one", where the computer, keyboard and its data storage device were combined in a single unit and sold with its own dedicated display monitor. Most home computers at that time such as ZX Spectrum series, Commodore 64, and BBC Micro relied on the use of the domestic television set and a separately connected tape recorder or disk drive. In itself, the all-in-one concept was not new, having been seen before on business-oriented machines and the Commodore PET.
The CPC 464 featured 64 KB RAM and an internal cassette deck. It was introduced in June 1984 in the UK. Initial suggested retail prices for the CPC 464 were 249.00/DM899.00 with a green screen and 359.00/DM1398.00 with a colour monitor. Following the introduction of the CPC 6128 in late 1985, suggested retail prices for the CPC 464 were cut by 50.00/DM100.00.
The CPC 664 features 64 KB RAM and an internal 3-inch floppy disk drive. It was introduced on 25 April 1985 in the UK.[7] Initial suggested retail prices for the CPC 664 were 339.00/DM1198.00 with a green screen and 449.00/DM1998.00 with a colour monitor.
After the successful release of the CPC 464, consumers were constantly asking for two improvements: more memory and an internal disk drive. For Amstrad, the latter was easier to realise. At the deliberately low-key introduction of the CPC 664, the machine was positioned not only as the lowest-cost disk system but even the lowest-cost CP/M 2.2 machine. In the Amstrad CPC product range the CPC 664 complemented the CPC 464 which was neither discontinued nor reduced in price.[8]
Compared to the CPC 464, the CPC 664's main unit has been significantly redesigned, not only to accommodate the floppy disk drive but also with a redesigned keyboard area. Touted as "ergonomic" by Amstrad's promotional material, the keyboard is noticeably tilted to the front with MSX-style cursor keys above the numeric keypad. Compared to the CPC 464's multicoloured keyboard, the CPC 664's keys are kept in a much quieter grey and pale blue colour scheme.
The back of the CPC 664 main unit features the same connectors as the CPC 464, with the exception of an additional 12V power lead. Unlike the CPC 464's cassette tape drive that could be powered off the main unit's 5V voltage, the CPC 664's floppy disk drive requires an additional 12V voltage. This voltage had to be separately supplied by an updated version of the bundled green screen/colour monitor (GT-65 and CTM-644 respectively).
The CPC 664 was only produced for approximately six months. In late 1985, when the CPC 6128 was introduced in Europe, Amstrad decided not to keep three models in the line-up, and production of the CPC 664 was discontinued.[9]
The CPC 6128 features 128 KB RAM and an internal 3-inch floppy disk drive. Aside from various hardware and firmware improvements, one of the CPC 6128's most prominent features is the compatibility with the CP/M+ operating system that rendered it attractive for business uses.
The CPC 6128 was released on 13 June 1985 and initially only sold in the US.[7] Imported and distributed by Indescomp, Inc. of Chicago, it was the first Amstrad product to be sold in the United States, a market that at the time was traditionally hostile towards European computer manufacturers.[10] Two months later, on 15 August 1985, it arrived in Europe[7] and replaced the CPC 664 in the CPC model line-up. Initial suggested retail prices for the CPC 6128 were US$699.00/299.00/DM1598.00 with a green screen and US$799.00/399.00/DM2098.00 with a colour monitor.
The redesign significantly enhanced the CPC hardware, mainly to rectify its previous shortcomings as a gaming platform. The redesigned video hardware allows for hardware sprites and soft scrolling, with a colour palette extended from a maximum of 16 colours (plus separately definable border) at one time from a choice of 27, increased to a maximum of 31 (16 for background and 15 for hardware sprites) out of 4096. The enhanced sound hardware offers automatic DMA transfer, allowing more complex sound effects with a significantly reduced processor overhead. Other hardware enhancements include the support of analogue joysticks, 8-bit printers, and ROM cartridges up to 4 Mbits.
The new range of models was intended to be completely backwards compatible with the original CPC models. Its enhanced features are only available after a deliberately obscure unlocking mechanism has been triggered, thus preventing existing CPC software from accidentally invoking them.[11]
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 Amiga and Mega Drive which was launched a few short months after the plus range. The plus range was a commercial failure,[12] and production was discontinued shortly after its introduction in 1990.
The 464 plus and 6128 plus models were intended as "more sophisticated and stylish" replacements of the CPC 464 and CPC 6128. Based on the redesigned plus hardware platform, they share the same base characteristics as their predecessors: The 464 plus is equipped with 64 KB RAM and a cassette tape drive, the 6128 plus features 128 KB RAM and a 3" floppy disk drive. Both models share a common case layout with a keyboard taken over from the CPC 6128 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 CPC 6128. As a result, a wide range of extensions for the original CPC range are connector-incompatible with the 464 plus and 6128 plus. 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 464 plus and the 6128 plus 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).[11] 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 CPC 6128's V3 firmware.[13]
Developed as part of the plus range, the GX4000 was Amstrad's short-lived attempt to enter the video game consoles market. Sharing the plus range's enhanced hardware characteristics, it represents the bare minimum variant of the range without a keyboard or support for mass storage devices.[11] It came bundled with 2 paddle controllers and the racing game Burnin' Rubber.
The KC compact [de] ("Kleincomputer" - which means "small computer" - being a rather literal German translation of the English "microcomputer") is a clone of the Amstrad CPC built by East Germany's VEB Mikroelektronik Mhlhausen, part of VEB Kombinat Mikroelektronik Erfurt, in October 1989. Although the machine included various substitutes and emulations of an Amstrad CPC's hardware, the machine is largely compatible with Amstrad CPC software. It is equipped with 64 KB of memory and a CPC 6128's firmware customized to the modified hardware, including a copy of Locomotive BASIC 1.1 modified in the startup banner only. The expansion port is a K 1520 bus slot. The KC compact is the last 8-bit computer introduced in East Germany.[19] Due to the German reunification happening at the time of the release only a very small number of systems were sold. The KC compact can be emulated by free software JKCEMU.[20]
In 1993, Omsk, Russia based company Patisonic released the Aleste 520EX, a computer highly compatible with the Amstrad CPC 6128.[21][22][23] It could also be switched into an MSX mode. An expansion board named Magic Sound allowed to play Scream Tracker files.
A BYTE columnist in January 1985 called the CPC 464 "the closest yet to filling" his criteria for a useful home computer, including good keyboard, 80-column text, inexpensive disk drive, and support for a mainstream operating system like CP/M.[24]
In order to avoid the CPU and the video logic simultaneously accessing the shared main memory and causing video corruption ("snowing"), CPU memory access is constrained to occur on microsecond boundaries. This effectively pads every machine cycle to four clock cycles, causing a minor loss of processing power and resulting in what Amstrad estimated to be an "effective clock rate" of "approximately 3.3 MHz".[26]
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