The Amstrad CPC 664
The CPC664 computer is built around the same architecture as the Amstrad CPC 464, but the aging tape drive was swapped out for a sequential disk drive system, the quick disk. This is the same disk drive that some of the later Spectrum computers used. It featured 3" disks, and data was written on them sequentially, making them not very fast compared to disk drives that used a random access format.
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