The Amstrad CPC (short for "Colour Personal Computer") is a series of 8-bit home computers made by Amstrad from 1984 to 1990. It was created to compete with other computers like the Commodore 64 and the ZX Spectrum. The CPC became popular mainly in the United Kingdom, France, Spain, and German-speaking areas of Europe, as well as in Canada.
The series included six different models: the CPC 464, CPC 664, and CPC 6128 were very successful in the European home computer market. Later models, such as the 464 Plus and 6128 Plus, were designed to help the system last longer with updated hardware. These models were not as successful, nor was the attempt to sell the Plus hardware as a game console called the GX4000.
The CPC computers used a Zilog Z80A CPU and had either 64 or 128 KB of RAM. Their design included a keyboard with built-in storage, such as a compact cassette deck or a 3-inch floppy disk drive. The main unit was sold with a monitor that was also used as the power supply. Many additional hardware options, like external disk drives, printers, and memory upgrades, were available for the CPC models.
The CPC series competed with other home computers used for playing video games. It had many game software options. The system was also appealing to business users because it was cheaper than other computers, had good quality black and white text and graphics, and could run CP/M software. This led to a wide variety of application software being developed for the CPC.
During its time, the CPC series sold about three million units.
Models
The CPC series of computers was designed with two main goals. First, the computers were made as "all-in-one" units, meaning the computer, keyboard, and data storage were combined into a single device. This unit came with its own dedicated display monitor. At the time, many home computers, such as the ZX Spectrum and Commodore 64, used a home television set and a separate tape recorder or disk drive. The idea of combining all parts into one unit was not new, as it had been used in business computers and the Commodore PET.
Second, Alan Sugar, the founder of Amstrad, wanted the CPC to look like a real computer, similar to those used in places like airports. He did not want it to resemble a "pregnant calculator," which was a term used to describe the small, membrane-style keyboards of the ZX81 and ZX Spectrum.
The CPC 464 was one of the most successful computers in Europe, selling over two million units. It had 64 KB of RAM and an internal cassette deck. It was released in June 1984 in the UK. The suggested retail price was £249.00/DM 899.00 with a green screen or £359.00/DM 1398.00 with a color monitor. After the release of the CPC 6128 in late 1985, the price of the CPC 464 was reduced by £50.00/DM 180.00.
In 1990, the 464 plus replaced the CPC 464, and production of the CPC 464 ended.
The CPC 664 had 64 KB of RAM and an internal 3-inch floppy disk drive. It was introduced in the UK on April 25, 1985. The suggested retail price was £339.00/DM 1198.00 with a green screen or £449.00/DM 1998.00 with a color monitor.
After the success of the CPC 464, customers asked for two improvements: more memory and an internal disk drive. Amstrad found it easier to add a disk drive. The CPC 664 was introduced as the lowest-cost disk system and the lowest-cost CP/M 2.2 machine. It was sold alongside the CPC 464, which was not discontinued or reduced in price.
The CPC 664 had a redesigned main unit to fit the floppy disk drive and a new keyboard layout. Amstrad described the keyboard as "ergonomic," with a tilted design and cursor keys above the numeric keypad. Unlike the CPC 464’s multicolored keyboard, the CPC 664’s keys were gray and pale blue.
The back of the CPC 664 had the same connectors as the CPC 464, except for an additional 12V power lead. The floppy disk drive required this extra voltage, which had to come from an updated monitor.
The CPC 664 was produced for about six months. In late 1985, when the CPC 6128 was introduced, production of the CPC 664 ended.
The CPC 6128 had 128 KB of RAM and a 3-inch floppy disk drive. It was compatible with the CP/M+ operating system, making it useful for business purposes. It was released on June 13, 1985, and sold only in the US at first. It was later introduced in Europe in August 1985, replacing the CPC 664. The suggested retail price was US$699.00/£299.00/DM 1598.00 with a green screen or US$799.00/£399.00/DM 2098.00 with a color monitor.
In 1990, the 6128 plus replaced the CPC 6128, and production of the CPC 6128 ended.
In 1990, Amstrad updated the CPC line by introducing new models called the "plus" range. The goals were to improve the hardware, redesign the case for a modern look, and add support for cartridges. The new models included the 464 plus, 6128 plus, and the GX4000 game console. The "CPC" label was removed from the model names.
The redesigned hardware improved the CPC’s performance, especially for gaming. The video system supported 16 hardware sprites and soft scrolling, with a color palette expanded from 16 to 31 colors. The sound system allowed for more complex effects with less processor use. Other improvements included support for analog joysticks, 8-bit printers, and cartridges up to 4 Mbits.
The new models were backward compatible with older CPC systems. However, new features required an unlocking mechanism to prevent accidental use by older software.
Despite these improvements, the plus range was seen as outdated because it used an 8-bit CPU. It failed to attract customers or software developers who were moving to newer systems like the Amiga and Mega Drive. The plus range was a commercial failure and production ended shortly after its release in 1990.
The 464 plus and 6128 plus models were designed to replace the older CPC 464 and 6128. They had the same base features: the 464 plus had 64 KB of RAM and a cassette drive, while the 6128 plus had 128 KB of RAM and a 3-inch floppy drive. Both models used a keyboard from the 6128 and had storage drives in separate compartments.
To simplify the EMC screening process, the edge connectors were replaced with micro-ribbon connectors, like those used on the German Schneider CPC 6128. This made older extensions incompatible with the new models. The 6128 plus also lacked a tape socket for external drives.
The plus range did not have on-board ROM, so firmware was provided via cartridges like Burnin’ Rubber and Locomotive BASIC. This reduced hardware localization costs and added a basic copy protection feature. However, differences in the V4 firmware caused issues with some older software, leading Amstrad to sell a cartridge with the original V3 firmware.
The 464 plus and 6128 plus models were introduced in 1990.
Reception
Your Computer stated that the CPC 464 had "better graphics and sound, a good version of Basic along with a flexible operating system" and that Amstrad's goal of selling 200,000 units by the end of 1984 was achievable.
A BYTE columnist in January 1985 described the CPC 464 as "the closest yet to meeting" his requirements for a useful home computer, which included a good keyboard, 80-column text display, an affordable disk drive, and support for a widely used operating system like CP/M.
Hardware
The Amstrad CPC computers use a Zilog Z80 processor that runs at 4 MHz. To prevent the CPU and video system from accessing memory at the same time and causing display issues, the CPU can only access memory at specific time intervals. This causes each memory cycle to take four clock cycles, slightly reducing the processor's speed. Amstrad estimated this made the effective clock rate about 3.3 MHz.
Amstrad CPC models come with either 64 KB (CPC 464, CPC 664, 464plus, GX4000) or 128 KB (CPC 6128, 6128plus) of RAM. Additional memory, up to 512 KB, can be added using third-party expansions. Some users also used experimental methods to add up to 4096 KB. Since the Z80 processor can only directly access 64 KB of memory, extra memory from 128 KB models and expansions is managed using a technique called bank switching.
The video system uses a combination of a CRTC (Motorola 6845 or compatible) and a custom gate array to create pixel displays. Later CPC 6128 models and Plus range computers combined the CRTC and gate array functions into a single ASIC.
Three display resolutions are available: 160×200 pixels with 16 colors (Mode 0, 20 text columns), 320×200 pixels with 4 colors (Mode 1, 40 text columns), and 640×200 pixels with 2 colors (Mode 2, 80 text columns). Larger screens can be created by reprogramming the CRTC.
The original CPC video hardware supports 27 colors using a 3-level RGB palette. The Plus range expanded this to 4096 colors using a 12-bit RGB system.
Except for the GX4000, all CPC models lack an RF or composite video output. Instead, they use a 6-pin RGB DIN connector to connect to the included Amstrad monitor. This connector provides 1v p-p analogue RGB with a 50 Hz sync signal that can drive a 50 Hz SCART television if connected properly. External RF adapters were available as first-party accessories.
The CPC uses the General Instrument AY-3-8912 sound chip, which has three channels that can produce square waves, white noise, or both. A limited set of volume control options is available.
Sound is played through a small (4 cm) built-in speaker with volume control, connected to an internal amplifier. Stereo sound can be output through a 3.5 mm headphone jack.
Digital sound samples can be played using a 5-bit resolution by sending data directly to the sound chip. This method is very demanding on the processor and difficult to use with other tasks. Examples include title screens in games like Chase H.Q., Meltdown, and RoboCop. Later Plus models added a DMA engine to handle this more efficiently.
Amstrad used Matsushita's 3" floppy disk drives, which were compatible with Hitachi's 3" format. These drives (built-in on later models) are single-sided and have 40 tracks. Users must remove and flip the disk to access the other side, each with its own write-protect switch. Each side is labeled "A" or "B" and typically stores 180 KB (in AMSDOS format) for a total of 360 KB per disk.
The drives use an NEC 765 FDC, the same as in IBM PC/XT, PC/AT, and PS/2 systems. Some features, like DMA transfers and single density support, were not used to reduce costs. Disks were stored in paper sleeves or hard plastic cases similar to compact disc jewel cases. These cases were more durable than 3.5 inch disks and could be mailed without extra packaging. A sliding metal cover protected the disk inside the case, unlike Sony's external cover. These disks were more expensive than 5.25 inch or 3.5 inch alternatives. Their low capacity and proprietary nature led to their discontinuation after the CPC itself was discontinued.
Other systems that used 3" disks included the Sega SF-7000, CP/M systems like the Tatung Einstein and Osborne machines, and embedded systems. Amstrad's PCW and ZX Spectrum +3 also used this format.
The Shugart-standard interface allows CPC machines to use standard 3", 3½", or 5¼" drives as secondary drives. Programs like ROMDOS and ParaDOS extend AMSDOS to support double-sided, 80-track formats, enabling up to 800 KB per disk.
On the CPC, 3" disks are called "discs," following the spelling on the machine's casing and British English conventions.
The hardware and firmware were designed to use external ROMs. Each ROM must be 16 KB and is connected to the memory space shared with video RAM. The firmware was created to allow easy access to new software from these ROMs. Popular applications, like word processors and programming tools, were sold on ROM (examples include Protext, Brunword, and MAXAM).
Extra ROMs are not inserted directly into the CPC but into external "ROM boxes" with sockets for the chips and minimal circuitry. These boxes were sold commercially or built by hobbyists and connected to the main expansion port. Software on ROM loads faster than from disks or tapes. The boot-up process checks for ROMs and can transfer control to them, allowing customization. However, most users were unaware of this feature unless they read technical materials, as it was not mentioned in manuals or marketing.
The machines also have a 9-pin Atari joystick port that can connect one or two joysticks using a splitter cable.
Peripherals
Amstrad made two RS-232-C D25 serial interfaces connected to the expansion port on the back of the machine. These interfaces included a through-connector for the CPC 464 disk drive or other devices.
The original interface included a Book of Spells, which helped transfer data between systems using a special method stored in the device’s ROM. It also had software to connect to British Telecom’s Prestel service. A different version of the ROM was made for the U.S. market because the commands "|SUCK" and "|BLOW" were not acceptable there.
Problems with the software and hardware of this interface led Amstrad to replace it with a version of a similar product made by Pace. Other companies, such as KDS Electronics and Cirkit, also sold serial interfaces.
Software
The CPC, like many home computers of that era, had its operating system and a BASIC interpreter stored in ROM. It used Locomotive BASIC, an improved version of Locomotive Software's Z80 BASIC designed for the BBC Micro co-processor board. It was especially notable for making it easy to use the computer's video and audio features, unlike the POKE commands needed on Microsoft systems. Other unique features included timed event handling using the AFTER and EVERY commands, and text-based windowing.
Digital Research's CP/M operating system was included with the 664 and 6128 disk-based systems, as well as the DDI-1 disk expansion unit for the 464. The 64k models came with CP/M 2.2, while the 128k models also included CP/M 3.1. The compact CP/M 2.2 version was stored mainly in the boot sectors of a 3" disk, called "System format." Typing |CPM from Locomotive BASIC would load code from these sectors, making it a common choice for custom game loading routines. The CP/M 3.1 version was stored in a separate file, which was then loaded from the boot sector. Many public domain CP/M programs were available for the CPC, including word processors like VDE and bulletin board systems like ROS.
Although compilers for Locomotive BASIC, C, and Pascal were available, most CPC software was written in native Z80 assembly language. Popular assemblers included Hisoft's Devpac, Arnor's Maxam, and DAMS in France. Disk-based CPC (not Plus) systems included an interpreter for the educational language LOGO, which was booted from CP/M 2.2 but had many features specific to the CPC, with much of its code stored in the AMSDOS ROM. The 6128 models also included a non-ROM version of CP/M 3.1. A C compiler was also developed and distributed in Europe through Tandy Europe by Micro Business products.
To create a recognizable mascot for the CPC, some games published by Amsoft, Amstrad's in-house software company, were labeled with the Roland name. However, these games were not originally designed around the Roland character, and the branding was added later. As a result, the character's design varied greatly, including a spiky-haired blonde teenager (Roland Goes Digging), a white cube with legs (Roland Goes Square Bashing), or a mutant flea (Roland in the Caves). Only two games, Roland in Time and its sequel Roland in Space, shared similar gameplay and character design. The Roland character was named after Roland Perry, one of the lead designers of the original CPC range.
Schneider Computer Division
Amstrad needed to sell its computers in Germany, Austria, and Switzerland, but did not have sales networks there. To solve this, Amstrad partnered with Schneider Rundfunkwerke AG, a German company known for selling affordable audio products. In 1984, Schneider created a separate company, the Schneider Computer Division, to handle the task. The Amstrad CPC computer models were then renamed and sold as Schneider CPC models in these countries.
Although the Schneider CPC models used the same hardware as the Amstrad CPC models, they had some differences. The Schneider CPC 464 and CPC 664 keyboards had grey keys instead of colored ones, but still followed the British keyboard layout. To match the German "QWERTZ" keyboard layout, Schneider provided software to rearrange the keys and stickers to label them. To meet stricter German electromagnetic compatibility rules, all Schneider CPC models included internal metal shielding. For the same reason, the Schneider CPC 6128 used micro ribbon connectors instead of edge connectors. These features, the grey keys and micro ribbon connectors, later appeared in later Amstrad CPC models.
In 1988, the partnership ended when Schneider refused to sell Amstrad's AT-compatible computers. Schneider sold the remaining Schneider CPC models and used its strong market position to introduce its own personal computer designs. Amstrad later formed a German company, Amstrad GmbH, to sell its products, including the CPC 464 and CPC 6128, but was unable to successfully build its own brand in German-speaking Europe.
Community
The Amstrad CPC was popular for a long time, mainly because it was used by businesses and for gaming. Programmers who were committed continued to develop software for the CPC, including graphical user interface (GUI) operating systems like SymbOS. Internet websites focused on the CPC have been created worldwide, offering forums, news, hardware details, software, programming resources, and games. Magazines about the CPC were published in the 1980s in countries such as Britain, France, Spain, Germany, Denmark, Australia, and Greece. These included the official Amstrad Computer User magazine, as well as independent publications like Amstrad Action, Amtix!, Computing with the Amstrad CPC, CPC Attack, Australia's The Amstrad User, France's Amstrad Cent Pour Cent, and Amstar. After production of the CPC ended, Amstrad allowed the CPC ROMs to be shared freely, provided the copyright message remains unchanged and that Amstrad is credited as the copyright holder. This gave emulator developers the ability to include the CPC firmware in their programs.
Influence on other Amstrad machines
Amstrad continued their success with the CPC 464 by introducing the Amstrad PCW word-processor series, another computer using a Z80 processor, a 3" disk drive, and software from Locomotive Software. The PCW was originally designed to work partly with an improved version of the CPC (called ANT, or Arnold Number Two—the CPC’s development name was Arnold). However, Amstrad chose to focus on the PCW, and the ANT project was never completed.
On 7 April 1986, Amstrad announced it had purchased from Sinclair Research "the worldwide rights to sell and manufacture all existing and future Sinclair computers and computer products, together with the Sinclair brand name and those intellectual property rights where they relate to computers and computer-related products." This included the ZX Spectrum and cost £5 million. The purchase also included Sinclair’s unsold stock of Sinclair QLs and Spectrums. Amstrad earned more than £5 million by selling these surplus computers. Amstrad later released two new versions of the Spectrum: the ZX Spectrum +2, based on the ZX Spectrum 128, with a built-in tape drive (like the CPC 464), and the following year, the ZX Spectrum +3, which included a built-in floppy disk drive (similar to the CPC 664 and 6128), using the same 3" disks as Amstrad CPC machines.