The Amstrad CPC 464 Plus
The Amstrad 464Plus is based on the architecture of the original Amstrad CPC464 but in a completely redesigned modern case. It was an effort to re-vamp the brand and create a computer that was aesthetically more pleasing than the large rectangular brick of the CPC464.
Amstrad CPC Computers
Amstrad was known for cheap hi-fi products but had not broken into the home computer market until the CPC 464. Their consumer electronic sales were starting to plateau and owner and founder Alan Sugar stated "We needed to move on and find another sector or product to bring us back to profit growth". Work started on the Amstrad home computer in 1983 with engineer Ivor Spital who concluded that Amstrad should enter the home computer market, offering a product that integrated low-cost hardware to be sold at an affordable "impulse-purchase price". Spital wanted to offer a device that would not commandeer the family TV but instead be an all-in-one computer with its own monitor, thus freeing up the TV and allowing others to play video games at the same time. Bill Poel, General Manager of Amsoft (Amstrad's software division), said during the launch press release that if the computers were not on the shelves by the end of June "I will be prepared to sit down and eat one in Trafalgar Square".
Many programs and peripherals were developed for the CPC computers. Amstrad's Operating System was AMSDOS. This OS is embedded in Basic using so-called RSX commands starting with |, but it could not format disks, for that you needed a special application. The 464 also could use CP/M 2.2 or 3.0 when used with an external Floppy disk unit (3" Hitachi, 180 KB / face). A lot of great CP/M software was adapted for the Amstrad CPC.
About 42 KB RAM was available for the user, the video memory and the ROM were mapped on the same addresses with a dedicated chip to switch the memory banks automatically.
The first Amstrad CPC prototype (called "Arnold", which gave the name ROLAND (Arnold acronym) to several CPC games) was built around a 6502 processor and then changed to a Z80 late in the computer’s development. A few months later, the CPC series would be completed with a computer which offered a built-in floppy disk unit: the CPC 664.
The CPC series are powered by the Zilog Z80 processor after the original attempts to use the 6502 processor, being used in the Apple II amongst many other 8-bit computer families, failed. The Z80 runs at 4 MHz, has 64K of memory and runs AMSDOS, Amstrad's own OS. The unit includes a built in tape drive and the choice of a colour or green monochrome monitor.
Normal Video Modes
- Mode 0 - 160x200 in 16 colors
- Mode 1 - 320x200 in 4 colors
- Mode 2 - 640x200 in 2 colors
- Mode 3 - 160×200 in 4 colors*
Each color can be chosen from a palette of 27 colors total. The dimensions in pixels given could be raised with clever use of FullScreen Trick (often dubbed erronuously as overscan mode). This then allows with a video memory of 24 KB (approximately) to have alternate video modes.
Alternate Video Modes
- Alt Mode 0 - 192x272 in 16 colors
- Alt Mode 1 - 384x272 in 4 colors
- Alt Mode 2 - 768x272 in 2 colors
Amstrad CPC Plus
In 1990, confronted with a changing home computer market, Amstrad decided to refresh the CPC model range by introducing a new range variantly labeled CPC Plus.
The main goals for the Plus range were:
- Enhancement to the existing platform
- Restyled case with a modern look
- Support for cartridge games
The redesigned video hardware allows for various upgraded features
- Hardware Sprites in 15 colors
- Soft scrolling
- Enhanced color palette: extended to 31 out of 4096.
Sound was also enhanced, including 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 an obscure unlocking mechanism has been triggered, 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.