Igor
CRISS is a 21st-century CP/M single-board computer based mainly on AVR microcontrollers. The CPU is a 20 MHz ATMEGA1284P, which imitates a 4 MHz Z80 through machine-code emulation. A pair of ATMEGA328s run the peripheral controller and a VGA output, so the CRISS can be used with modern monitors. Standard image is monochrome green-on-black, looking instantly familiar to users of Kaypro's, Osborne's and other contemporary CP/M machines. Starting from May 2023 VGA module was enhanced with the additional circuit based on ATTINY84 MCU and 4-bit shift register that colorizes video to the 8 colors!
Software is loaded through an SD card that holds floppy images. The CRISS can directly run programs written for the Kaypro II and Robotron 1715 computers, although other platforms can be supported as well with a software upgrade.
Housed in a neat little case (13x10cm PCB size), the CRISS can communicate with standard PS/2 keyboards and serial printers. Even an Ethernet port is provided for those willing to experiment with network connectivity (a rare feature in the 1980s).
The basic idea was to build really 8-bit computer that would use modern technologies and components. CRISS CP/M did it!
Now AVR runs BASIC, TURBO PASCAL, C, FORTRAN etc., plays TETRIS, ZORK 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).
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!
It is great example how your CRISS CP/M workspace may look like! Thanks to GinDiamond
Blake W. Ford
Augusto Baffa
Dessislav Gouzgounov
jessexm
This system emulates a Z80. One can emulate a Z80 under windows faster and easier. Why not get a HP EliteDesk 800 G2 Desktop (refurb)? It is about the same size and costs about $100. It has 16GB of RAM and 240GB of SSD and comes with Win10 Pro. Just load SIMH Z80 and it is done.