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MK-90 emulator

The program emulates a PDP-11 compatible CPU and uses a ROM dump from the original calculator, therefore it should function almost exactly like the real one.
It works on PC-compatible machines with Microsoft Windows operating system.

Files to download

Program version 22, updated 2022/02/01

download - Delphi sources

download - compiled executable

Usage: extract the files into an empty directory, then run the program mk90.exe - ROM image of an earlier MK-90 version with BASIC V1.0

Usage: replace the file rom.bin
Note: after the ROM change the memory modules should be reformatted with the command INIT.

The screenshots

Screenshot of the MK-90 emulator

The debug window of the MK-90 emulator

Usage hints

Integrated debugger

Disassembly box

Binary Editor box

Registers box

Program execution control

The mk90.ini file

Some parameters of the emulator can be customised by editing the mk90.ini file with any text editor.
Description of the contents of this file:

This setting controls the emulated CPU execution speed (number of instructions executed every 10ms).
This setting defines the physical size of emulated RAM. It is intended for test purposes only! The default value shouldn't be modified, because the system supports only fixed RAM size of 16kB. Since the entire address space is occupied, the extra RAM takes precedence over the ROM containing the test routines.
This setting changes the base of the numeral system used by the debugger (16 for the hexadecimal system, 8 for the octal system).
Value other than 0 invokes on program exit a file dialog that allows the user to save the modified ROM image.


To uninstall the emulator, simply delete the directory where it was installed. The program doesn't modify anything outside its installation directory.


Known limitations and issues of the current version

File copy utility

download - file size: 19kB, sources and executables, DOS and Windows (in a DOS window)

The archive contains two separate programs for each BASIC version: - for BASIC version 1.0 - for BASIC version 2.0

The utility copies a list of BASIC programs in ASCII format (cyrillic characters are expected to be encoded in Windows-1251) specified in the command line to the MK-90 cartridge memory image. Example: prog1.bas [prog2.bas prog3.bas ...]

As a result an output file SMP0.BIN is created, which can be used by the emulator or written into a real cartridge.

To load a program in BASIC 2.0 use the command LOAD with the parameter A, for example: