The basic idea was to build really 8-bit computer that would use modern technologies and components. CRISS CP/M did it! 8-bit MCUs only, standard keyboard, monitor and LAN can be used, CP/M OS provides compatibility with the standard software, LAN and other "modern" features are incorporated into the BIOS and accessible with just few lines of code from a user program!
Single-board design, AC/DC PSU is on the board, standard sockets, DIP components only, and just 13x10cm PCB size!
Now AVR runs BASIC, TURBO PASCAL, C, FORTRAN etc., plays TETRIS and other games, makes text processing, runs spreadsheets and much more. CP/M software world is much wider than it is usually imagined and CRISS can "switch" the platform on the fly without rebooting!
All videos are from the real device, no emulation! :)
As a component base the line of the Microchip (Atmel) AVR family was chosen as a reliable and honest 8-bit platform. All interfaces are implemented using specialized microcircuits. Internal frequency is 20 MHz, Z80 emulation corresponds to the 4MHz z80 CPU, 1us register-to-register operation time.
The computer is built following the classic structure: the central processor is implemented using the ATMEGA1284P and emulates Z80 CPU with extended commands set, the peripheral controller is built on the ATMEGA328P, the VGA controller is built on the ATMEGA328P and ATTINY13 without overclocking(!), the Ethernet controller is ENC28J60 (Microchip), RTC is DS1305 (Dallas), the RAM 64Kx8 is W24512 (Winbond) but 128kB chips also can be used.
Internal SPI bus with the address decoder allows easily add additional peripheral device: CAN bus etc, such devices are accessible via IN/OUT commands from the user programs in any language.
100% open project, send me requests for any info, DIY kits and assembled boxes are also available!